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STEAM POWER PLANTS 



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electrical World The Engineering and Mining' Journal 

Ingineering Record American Machinist 

Jectric Railway Journal Coal Age 

Metallurgical and Chemical Engineering Power 



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ENGINEERING RECORD SERIES 



STEAM POWER PLANTS 



THEIR DESIGN AND CONSTRUCTION 



BY 



HENRY C. MEYER, Jr., M.E. 

Consulting and Mechanical Engineer 



THIRD EDITION 
Entirely Rewritten and Enlarged 



McGRAW-HILL BOOK COMPANY 
239 WEST 39TH STREET, NEW YORK 

6 BOUVERIE STREET, LONDON, E. C. 
1912 



-\ 






Copyright, 1902, by THE ENGINEERING RECORD 
Copyright, 1905, by McGRAW PUBLISHING COMPANY 
Copyright, 1912, by McG RAW-HILL BOOK COMPANY 






Stanbope flbress 

F. H.GILSON COMPANY 
BOSTON, U.S.A. 



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■CLA303981 

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INTRODUCTORY NOTE 

(TO THE FIRST EDITION) 



Frequently engineers and others in charge of a manufacturing 
business, be it a mill, factory or electric generating station, are 
called upon to design and purchase a steam power plant or parts 
of it when their knowledge of the machinery that goes into such a 
plant is more or less limited, and without being able to obtain the 
benefit of the advice of a competent consulting engineer. It is 
hoped that this book will be of special value to this class and of 
some value to all interested in steam power-plant construction. 
Part of the text appeared in a series of articles in The Engineer- 
ing Record, and when the demand for them seemed to warrant 
their being published in book form they were thoroughly revised 
and considerable new matter added. A number of the illustrations 
have been selected from articles printed in The Engineering 
Record during the last two or three years descriptive of steam 
power-plant construction. They are reprinted without the text 
that accompanied them, thinking they would be suggestive. 



INTRODUCTORY NOTE 

(TO THE THIRD EDITION) 



Shortly after this book was written in 1902, the author began 
to practice as a consulting engineer for power-plant design and 
construction, and, upon revising the work for the edition appearing 
in 1912, the experience gained has led to some changes and many 
additions. The chapter on turbines has been added, also much 
new matter upon the subject of steam piping, condensers, and 
chimneys. Other parts of the book have been added to and 
brought up-to-date and a number of new illustrations are presented. 

H. C. M. 

New York, January, 1912. 

v 



CONTENTS. 



Page 

Inteoductory Note v 

CHAPTER I. 

Design of Steam Power Plants 1-14 

Location of Plant — Drawings — Type of Power House — 
Building — Foundations — Engine Foundations — Operating Ex- 
penses — Cost of Power-plant Equipment. 

CHAPTER II. 

Proportioning Steam Boilers 15-26 

Heating Surface Necessary — Value of Boiler Horse-power — 
Advantages of Types of Boilers — Division of Heating Surface in 
Units — Importance of Proper Grate Surfaces — Proportioning 
Grate — Coal — Semibituminous Coals — Bituminous Coals — 
Anthracite Coal. 

CHAPTER III. 

Design of Horizontal Return Tubular Boilers and Boiler In- 
spections 27-47 

Thickness of Shell — Braces — Supporting Boilers — Tubes — 
Riveting — Boiler Settings — Boiler Specifications — Smoke Flue 
and Chimneys — Specifications for Water-tube Boilers. 

CHAPTER IV. 

The Selection of the Types of Engines, Dimensions of Cylin- 
ders, Speed, Steam Pressure, etc 48-67 

Selection of Type — Steam Pressure — Rotative Speed — Mean 
Effective Pressure — Piston Speed — Mean Effective Pressures for 
Simple Engines — Proportioning Cylinders of Single-cylinder Cor- 
liss Engine — Proportioning Cylinders for Single-cylinder, High- 
speed Engines — Proportioning Cylinders for Medium-speed 
Engines — Proportioning Cylinders for Compound Engines — En- 
gines with Variable Loads and Overload Capacities — Superheated 
Steam, Steam Jackets, and Reheaters. 

CHAPTER V. 

Specifications for Steam Engines 68-88 

CHAPTER VI. 

Turbines 89-101 

Advantages of Turbines — Attention — Space Conditions — 
Absence of Oil — Overload Capacity — Variable Loads — Dur- 
ability — Relative Operating Costs — Effect of Vacuum and Steam 
Pressure — Exhaust- steam Turbines — Specifications. 

vii 



viii CONTENTS 

CHAPTER VII. 

Page 

Arrangement of Steam and Water Piping 102-122 

Drawings — Principles Involved — Exhaust Piping for Con- 
densing Plants — Piping between Cylinders of Compound En- 
gines — Exhaust Piping for Noncondensing Plants — Piping for 
Building Power Plants — Care of Drips — Feed-water Piping — 
Blow-off Piping. 

CHAPTER VIII. 

Materials for Piping, Pipe Sizes, Separators, and Oiling Sys- 
tems . 123-140 

Kind of Pipe — Size of Steam Pipes — Kind of Fittings — Speci- 
fications for Piping — Valves — Pipe Hangers — Covering Pipes 

— Grease Separator — Steam Separators — Steam Traps — En- 
gine Oiling Systems. 

CHAPTER IX. 

Condensers and Pumps 141-159 

Saving Due to Condensers — Condensers — Type of Condenser 

— Location of Condensers — Water Necessary for Condensers — 
Sources of Water Supply for Condensers — Cooling Towers — 
Specifications for Condensers — Guarantees — Boiler-feed Pumps. 

CHAPTER X. 

Feed- water Heaters and Economizers 160-168 

Value of Feed-water Heaters — Types of Heaters — Uses for 
Heaters — Condensation in Heaters — Purchasing Heaters — 
Economizers. 

CHAPTER XL 

Mechanical Draft 169-180 

Theory of Combustion — Necessity for Ample Draft — Me- 
chanical Draft — Advantages of Mechanical Draft — Theory of 
Fans — Design of Fans. 

CHAPTER XII. 

Chimneys 181-202 

Size of Chimneys — Height of Chimneys — Draft — Capacity 
of Chimneys — Thickness of Chimney Walls — Chimney Linings, 
etc. — Materials — Masonry Chimney Foundations — Steel Chim- 
neys — Foundations for Self-supporting Steel Chimneys. 

CHAPTER XIII. 

Coal Handling, Water Supply, and Purification 203-214 

Coal-handling Machinery — Cost of Coal Handling by Ma- 
chinery — Cost of Boiler-room Labor — Mechanical Stokers — 
Burning Pulverized Fuel — Supply of Boiler Water — Water 
Softening — Purifying with Exhaust Steam — Purifying by Live 
Steam — Purifying by Chemical Treatment. 



STEAM POWER PLANTS. 



CHAPTER I. 
THE DESIGN OF STEAM POWER PLANTS. 

No better service can be done the non-expert about to con- 
struct a steam plant than to advise him to engage at the outset of 
the project some capable engineer to design the plant and super- 
intend its installation. In spite of the advantages of having 
work planned and carried out by such men, it will always be, 
probably, that a very considerable proportion of the work done 
will be constructed, for one reason or another, by persons with a 
semitechnical training without the aid of the expert engineer. 
It is, therefore, proposed to give data and information which, it 
is hoped, will aid the engineer who cannot be called an expert, in 
selecting the various kinds of machinery and apparatus that make 
up a steam power plant; to discuss specifications for these in a 
general way; and, in some instances, to outline the manner in 
which they should be purchased. 

It is the practice of many engineers in steam-plant construction 
to invite bids on apparatus described very generally in a specifica- 
tion and intended to perform a service under conditions that are 
named, the idea of the engineer being to allow each bidder to pro- 
portion the parts of the apparatus he is to furnish and to quote 
a price on it. When bids are received under these conditions, it 
generally follows that there is a variation in the size of the ma- 
chinery offered by different makers to do the same work, and the 
lowest in price may not be best adapted for the conditions. An 
engine, boiler, or pump, in fact almost everything about a steam 
plant, may do the work required of it, but it may be so propor- 
tioned as to do it in a manner that is not best for the owner. For 
instance, while an engine may give the required power, its cylin- 
ders may be so small that it requires an excessively large amount 
of steam to run it, or a boiler may be so small that an abnormal 

1 



2 STEAM POWER PLANTS 

amount of coal must be burned in order to generate the steam 
required. The expert engineer is, of course, able to detect and 
reject bids on deficient apparatus, yet when the size of the ap- 
paratus is fixed by the contractor it may happen that the pur- 
chaser, who is not an expert, will accept machinery which is not 
best adapted for the service that it is to perform, particularly if 
the too frequent custom of purchasing the apparatus lowest in 
price is followed. 

There are other methods of buying apparatus for a steam plant. 
One is to go to a reputable manufacturer or contracting engineer 
and engage him to build the machinery wanted and pay what is 
asked for it. Such a contractor should not, however, be placed 
in competition with others if he is to design a plant to fill the re- 
quirements of the owner; for if this is done the contractor's in- 
terest is to design a cheaper plant than will be proposed by his 
competitor, whose bid is based on the plant designed by him, and 
this kind of competition sometimes results in inferior apparatus 
being supplied. 

Another method of purchasing is to have the engineer state in 
his specification the dimensions of the apparatus wanted, permit- 
ting, however, a departure from these specified dimensions in 
order that a manufacturer can make use of his standard patterns, 
provided such a course is not detrimental to the purchaser's in- 
terest. When all manufacturers bid on the same basis their bids 
are lower and the purchaser is sure of getting a properly propor- 
tioned machine, provided the engineer who prepares the plans 
and specifications is capable. Many believe the last two methods 
of procedure much preferable to the first. Latitude given an im- 
prudent contractor, in the way of fixing the dimensions of the 
apparatus he is to supply, may, in a measure, be covered by 
demanding a guarantee as to efficiency; yet tests necessary to 
determine if the guarantees are fulfilled are expensive and are 
therefore generally omitted. 

Location of Plant. — One of the first questions to be decided in 
the construction of a power plant is its location. This depends 
on several factors, the most important of which are, the ease with 
which the power may be transmitted from the generating source 
to the locations of the demand, the cost of delivering coal and 
removing ashes from the power house, and the availability of a 
supply of water for condensing purposes. 



STEAM POWER PLANTS 3 

The first factor, the ease with which power may be transmitted 
from the generating source to the machines utilizing it, is the one 
that frequently decides whether an electric or belt-and-shafting 
system of transmission is to be used. It is, of course, impossible 
to give any general rule applicable to all cases, as each situation 
demands a thorough investigation of the cost of installing and 
operating both plants. In arriving at their relative costs of opera- 
tion, the interest on the investments, the repairs, the fuel cost, the 
cost of attendance, supplies, etc., have to be reckoned. Generally 
speaking, it may be said that in any situation where the load on 
the power plant is practically constant throughout the working 
day, as in a textile mill, and where the power house may be 
located close to the lines of shafting so that belts may be carried 
from the engine to the shafting without the use of gearing, 
quarter-turn belts, etc., the belt-and-shafting system of transmis- 
sion seems the most favored. If, however, the manufacturing 
establishment consists of a number of separate buildings in which 
lines of shafting are at different angles, so as to require several 
separate power plants or else a complicated system of belts or 
gears, the electric system possesses advantages as regards cost 
of operation that make its adoption advisable. Again, in estab- 
lishments where the work is similar to that of a large machine 
or bridge shop, where the tools are used intermittently, where 
one or two departments may run overtime, the electric system 
is rapidly gaining friends. The reason for this is not the dif- 
ference in the operating expenses, which are slight, inasmuch 
as a machine shop requires a very small amount of power for 
its operation, but in the greater convenience and cleanliness of 
the electric system. One solution of the problem of transmitting 
power when shafts lie in directions that are not parallel is the rope 
drive. This has been used with the greatest success in many 
plants. Its low first cost and cost of repairs and the flexibility 
of the system make it well worth considering in many installa- 
tions. 

The cost of handling coal and removing ashes in a power house 
may be a considerable item in the operating expenses, and large 
plants are therefore usually equipped with coal-handling ma- 
chinery. Some steam plants are so arranged that railway cars or 
coal cars may be run over a receiving hopper from which the coal 
is conveyed mechanically to storage bunkers over the boilers and 



4 STEAM POWER PLANTS 

chuted from the bunkers to the furnaces by gravity. If a plant is 
not to be provided with coal-handling machinery, it is well, if 
convenient, to provide a trestle so that cars may be run over and 
dump into a bunker opposite the furnace doors in order that the 
coal may fall by gravity through holes in the wall separating the 
bunker from the boiler room, onto the floor of the latter, in front 
of the furnace doors. 

The value of water in sufficient quantity to condense the steam 
exhausted by the engines often determines the location of the 
power house. From 15 to 20 per cent of the fuel used by a non- 
condensing engine will be saved if it is operated with a condenser. 
Each pound of steam exhausted by an engine requires a supply of 
30 to 35 pounds of water for the condenser, so it will be seen that 
the water needed for condensing purposes is often a considerable 
quantity. Sometimes when a power house cannot be located on 
the bank of a stream from which a supply for this purpose is 
available, a pipe or conduit can be laid from a river to a well near 
the power house, the grade of the conduit being below that of 
minimum low water. The injection pipe, as the pipe that conveys 
the water to the condenser is called, can then be run from this 
well to the condenser, which is usually located close to the engine. 
Because of the vacuum in the condenser, the water will rise in the 
injection pipe from a lower level to the condenser. It is not ad- 
visable, however, to attempt to lift the injection water over 20 
feet. Where the lift would be slightly greater than this the con- 
denser can be placed in a pit. Since the development of the cool- 
ing tower, an apparatus for cooling condensing water so that it 
can be used over and over again, condensing plants are not so de- 
pendent on an abundant water supply as they were before this 
apparatus was perfected; hence the importance of locating a 
plant by a stream for condensing purposes is not so great as it 
was once. 

Drawings. — Complete and accurate drawings of all of the de- 
tails of a steam plant are a necessity. It is well to make assem- 
bled drawings showing the plant in plan and as many elevations as 
may be necessary to make the arrangement perfectly clear. As- 
sembled drawings insure all parts of the plant fitting together 
properly, and prevent mistakes such as attempting to run steam 
pipes where a building column ought to be, and so on. If as- 
sembled drawings are to be made, the scale assumed should be 




Plate i. — Lincoln Wharf Power Station, Boston Elevated Railway Co. 

GEORGE A. KIMBALL, CHIEF ENGINEER; SHEAEF & JAASTED, CONSULTING ENGINEERS. 



STEAM POWER PLANTS 5 

sufficiently large to show the steam-pipe system. Three-eighths 
of an inch to the foot is about as small as can well be used. As 
soon as contracts are made for engine, boilers, feed-water heaters, 
pumps, etc., accurately dimensioned blue-prints showing the 
machinery in plan and elevation should be obtained from the 
contractors. Experience has shown that it is well, with some 
firms at least, in order to avoid delay, to get these blue-prints 
before the contracts are let. Contracts for the building, steel- 
work, etc., should not be made until the machinery is contracted 
for, since it may not be possible to obtain the machinery which 
was contemplated at the time the building plans were made, and 
machinery then available may not fit. It is, of course, essential 
that the building be fitted to the machinery, not the machinery 
fitted to the building. 

Type of Power House. — Generally the relative location of the 
engine and boiler rooms is determined by some local condition. 
Where it can be done, however, it is better to locate the engine 
and boilers in one building, with a wall between them, and to 
place them in parallel rows with the cylinders of the engine adja- 
cent to the rear of the boilers. This is particularly the best ar- 
rangement if the plant is likely to be enlarged in the future. The 
steam pipe connecting the boiler and engine or engines is the most 
direct in this arrangement, and it can be most readily enlarged. 
If the engine and boiler houses are placed end to end and con- 
tain two or more boilers supplying one engine, the proper size of 
piping for such a plant will be inadequate if another engine is 
added at one end of the plant and more boilers installed at the 
other. 

Where land is very expensive, boilers are sometimes placed 
in buildings on two or more floors. Ordinarily, however, the 
boiler-room floor is usually on the level with the outside ground, 
while the engine-room floor with large engines is invariably higher, 
usually from 6 to 12 feet or more, depending on the height of 
the engine foundations. Sometimes an engine is installed where 
the engine-room floor is on the ground level. When this is 
done, it is necessary to construct a pit for the condenser, if such 
an auxiliary is used, also pipe trenches, and, if the engine is a large 
one, a pit for the flywheel. It perhaps ought to be stated at this 
time that a condenser ought always to be below the engine, as the 
pipe leading to the condenser cannot rise at any point without 



6 STEAM POWER PLANTS 

introducing a dangerous element into the power plant. The 
arrangement that necessitates the construction of pits ought to be 
avoided, if it is possible, as it is difficult to construct a water-tight 
pit for the flywheel and condenser, because the vibration of the 
engine is apt to crack the lining of the pit and allow water to enter, 
if there is any in the soil. The trenches for the exhaust piping 
have to be covered and the piping is not nearly so accessible when 
in a covered trench as it is when in the basement usually provided 
under engine rooms. 

Building. — A building for a power house should, if possible, 
be constructed of fireproof materials. Brick walls with steel 
trusses supporting a wooden roof covered with tar and gravel, or 
with some form of fireproof construction, is the usual construc- 
tion. The brick walls sometimes carry the roof trusses and tracks 
for traveling cranes, and again these are supported by steel col- 
umns resting on the foundations and imbedded in the brick walls, 
the latter, however, carrying only their own weight. The build- 
ing should be designed by an architect or structural engineer. 
The construction of the building can be done by bridge shops 
making a specialty of constructing buildings of this character and 
supplying the steelwork for them. 

The buildings should be of such a size that the machinery in 
them is not cramped. When there are several machines in an 
engine room, it should be remembered when locating them that it 
is sometimes necessary to stop a machine very quickly. It is 
well, therefore, to place all machinery in such a position that it is 
readily accessible to the man or men in charge of it. Provision 
should be made, in planning and constructing a power house, for 
bringing the machinery into the building after it is erected, and a 
door of sufficient size to admit the largest part of a machine must 
be provided. Ample room must be left around the horizontal 
steam and water cylinders to be able to remove piston rods if 
it should be necessary, without removing the cylinder from its 
foundations. Enough space must be left between the founda- 
tions of adjacent engines and between foundations and engine- 
room walls to allow a man to get between them to reach the 
foundation bolts. In a boiler room, there must be a clear space 
in front of the boilers at least as wide as the boiler tubes are long. 
The distance between the rear of the boilers and the wall need not 
be greater than 5 or 6 feet, or enough to allow a wheelbarrow to 



STEAM POWER PLANTS 




Plan. 



Fig. 1. Electric Power Station designed by Dean & Main. 



8 



STEAM POWER PLANTS 



be placed opposite the soot door in the rear of the boiler setting, 
if such a door is provided. 

Foundations. — The character of the soil underlying the site for 
a power house should be carefully examined in order that the 



mmAmmmmMM% 




no.2 

Fig. 2. Piping in Power House. (Lockwood, Greene & Co., Engineers.) 



foundations can be so planned as to keep the load imposed by the 
buildings and machinery within the safe limit. For ordinary one- 
story buildings where the loads are not excessive, holes should be 
dug at numerous points over the site and the character of the soil 



STEAM POWER PLANTS 9 

determined. As the magnitude of the work increases more care 
should be taken. In important work a competent specialist in 
foundation work should be consulted. As to the bearing capacity 
of different soils, the New York Building Code states: " Different 
soils, excluding mud, at the bottom of the footings shall be 
deemed to safely sustain the following loads to the superficial 




8" W. I. Pipz. r \ftJ5CJ 




Fig. 3. Section Main Steam Piping, Lincoln Wharf Station. 



foot, namely: Soft clay, one ton per square foot; ordinary clay 
and sand together, in layers, wet and springy, two tons per square 
foot; loam, clay, or fine sand, firm and dry, three tons per square 
foot; very firm, coarse sand, stiff gravel or hard clay, four tons 
per square foot." 

If loose rock is found it should be removed; solid rock should 
be dressed off in steps with vertical risers and horizontal treads 



10 STEAM POWER PLANTS 

so that the pressure will be exerted everywhere in a vertical di- 
rection. Solid rock will stand almost any k\ad that can be im- 
posed upon it. If soil of low bearing power is found, piling is 
usually resorted to. Piles may be of spruce or hemlock, at least 5 
inches in diameter at the point and 10 inches in diameter at the 
butt for piles 20 feet or less in length, and 6 inches at the point 
and 12 inches at the butt for piles over 20 feet in length. The 
bearing power of piles not driven to rock or hardpan or similar 
firm material may be calculated by the Wellington formula, in 
which the safe bearing power in tons is equal to twice the weight 
of the hammer in tons multiplied by the height of the fall in feet 
divided by one plus the penetration of pile under the last blow 
in inches. From a knowledge of the total load to be carried and 
the load that each pile will support, the number of piles necessary 
under a weight to be supported can be calculated. If the soil is 
not firm, the bearing power of a pile should be taken much less 
than that given by the formula, in order to allow for decrease in 
strength due to vibrations of the machinery. To avoid decay the 
piles should be cut off at the level of the ground water or not 
more than one foot above it. 

It is getting to be the practice in power-house construction 
where piles are used, to saw off the heads of the piles to a uniform 
grade, then excavate the materials between the heads of the piles 
for a depth of a foot or so and lay a bed of concrete sometimes 
several feet in thickness between the heads of the piles and over 
their tops. An 8-foot bed of concrete over piles on 30-inch cen- 
ters was used as a foundation for the 96th Street power house of 
the Metropolitan Street Railway Company in New York City. 
If the soil underlying a power-house site is found to possess too 
low a bearing power for the foundations of the engines and boilers 
to be constructed directly on it, concrete beds may be laid so 
as to distribute the load. Sometimes a concrete bed is laid under 
the engine foundations and another under the boilers. Again, 
the entire site is covered with a bed of concrete and the wall 
footings and machinery foundations built directly upon it. 

Engine Foundations. — These are almost invariably con- 
structed by the owner, the engine builder furnishing the draw- 
ings. The latter generally consist of accurately dimensioned 
drawings showing the foundations in plan and one or two eleva- 
tions, and also a drawing of a board template which has to be 



STEAM POWER PLANTS 11 

made for locating the foundation bolts. A hole is bored in the 
template where each bolt is located, and the template is supported 
over the place where the foundation is to be constructed, at such 
a height that the foundation bolts may be suspended in the 
position that they will finally occupy, by passing them through 
the holes in the template, the nut on the upper end holding them 
in position. The foundation is then built around the bolts, leav- 
ing holes about them an inch or two greater in diameter than 
the bolts themselves, so that the latter may be moved slightly, to 
pass through the holes in the engine bed plate, should an error 
occur in locating the position of the bolts or the holes in the 
engine bed. 

Foundations for engines are sometimes constructed on a very 
thick bed of concrete, as has been explained. This is not always 
necessary, and, where good loam and clay are -known to exist for 
some distance below the surface of the ground, the earth may be 
leveled off and the foundation commenced on a layer of concrete 
just thick enough to give a good bearing. If loose rock or poor 
earth is found, this should be removed and the excavation filled 
with concrete, in which loose stones, old bricks, etc., may be im- 
bedded, care being taken to put them in layers alternating with 
the concrete, which should be so placed and rammed as to make 
sure that there are no voids. This should be continued up to the 
level at which the regular brick or concrete foundations are to 
commence. There seems to be no good reason for using a pure 
concrete bed if the earth is of good quality and the load imposed 
upon it not excessive. Engine foundations should be of brick 
laid in cement mortar made of one part Portland cement to two 
parts clean sharp sand or of concrete. Good concrete is obtained 
by mixing one part good Portland cement, two parts sand, and 
four parts broken stone, the latter small enough to pass through a 
2-inch ring. Concrete should be laid in layers not over 6 inches 
thick, each layer being thoroughly rammed before the one above 
is put down. Such a foundation has to be surrounded with board 
walls or forms to suitably hold the concrete while it is being laid. 
A Portland cement concrete foundation ought to stand at least 
two months, and one of brick in Portland cement one month be- 
fore it is loaded, whenever possible to spare the time ; but if suit- 
ably proportioned and carefully watched it can be safely loaded 
much sooner, especially if the concrete is made as dry as possible. 



12 STEAM POWER PLANTS 

Operating Expenses. — The cost of operating a plant includes 
the cost of fuel and removing ashes if coal is used, the cost of 
water, oil, waste, attendance, the cost of repairs necessary to 
keep the equipment in running condition, and the fixed charges. 
Fixed charges include the interest on the money invested, 
insurance, taxes, and depreciation. An allowance of 2 per cent 
of the cost of apparatus will ordinarily be sufficient to cover 
ordinary repairs. The rate of interest will be from 4 \ to 6 per 
cent, depending upon the value of money to the owners. An 
allowance of 2 per cent ought to cover both insurance and taxes, 
although insurance is not always carried. 

It is customary in establishing a sinking fund to assume, in 
fixing the rate of depreciation, that a certain percentage of the 
original cost of power-plant apparatus shall be set aside or 
charged off each year to cover depreciation, and that each amount 
so treated will draw interest so that the total of the amounts so 
set aside plus the interest return on each will aggregate a sum 
sufficient to renew the apparatus at the end of its estimated life. 
To fix the rate of depreciation upon power-plant apparatus means, 
therefore, the determination of its useful life, and this is a very 
difficult matter to determine in many cases. The life of such 
apparatus is determined by its quality, that is, whether it is the 
best of its kind or of inferior manufacture, by the care and 
attention given it, by the use to which it is subjected, that 
is, whether it is run hard or moderately. In many cases the 
life depends mainly upon whether the equipment will become 
sufficiently obsolete as to require replacement before it is worn 
out. The depreciation in large central electric supply stations 
was very great in the several large cities in the United States 
during the period from 1895 to 1905. At the beginning of that 
period several cities were supplied with electricity by direct- 
current stations operating at low voltage, which required the use 
of a comparatively large number of stations scattered over the 
area supplied. The development of alternating-current electri- 
cal machinery, in large units, made possible a great reduction in 
operating expenses; and this fact, coupled with the growth of 
the business, caused the abandonment of many direct-current 
stations after only a few years' use and the installation of new 
generating equipment in one or at most comparatively few very 
large stations supplying the entire area with alternating current 



STEAM POWER PLANTS 



13 



transformed into direct current by suitable converting apparatus 
at points where direct current was formerly generated. In fact, 
all electric supply stations are subject to high rates of depreciation 
on account of the generally rapid increase in business which 
requires the abandonment of plants for the more economically 
operated larger ones. In certain classes of work, as in mills and 
factories, where this condition does not hold, and in office build- 
ings, which are rarely increased in size, power-plant apparatus 
may enjoy a much longer period of usefulness. Under the latter 
condition the life of power-plant apparatus may be considered to 
lie within the limits given in Table 1, depending upon the quality 
of apparatus used, the care given it, and the manner in which 
it is used. 



TABLE 1. — LIFE OF POWER-PLANT APPARATUS. 



Buildings, masonry 

Chimneys, masonry. 

Chimneys, iron 

Boilers, water-tube 

Boilers, fire-tube 

Engines, Corliss slow-speed 
Engines, medium-speed. . . . 

Engines, high-speed 

Turbines 

Pumps and condensers 

Coal conveyors 

Piping 

Electrical generators 



Years. 



40-50 
40-50 
10-20 
20-30 
15-20 
20-30 
15-20 
10-15 
20-25 
15-20 
10-15 
10-20 
15-25 



TABLE 2. — RATE OF DEPRECIATION. 









Rate of interest, pei 


■ cent. 






Life in 
years. 






























3.0 


3.5 


4.0 


4.5 


5.0 


5.5 


6.0 


5 


18.83 


18.65 


18.46 


18.28 


18.10 


17.91 


17.73 


10 


8.72 


8.52 


8.33 


8.14 


7.95 


7.76 


7.58 


15 


5.37 


5.18 


4.99 


4.81 


4.63 


4.46 


4.29 


20 


3.72 


3.53 


3.36 


3.19 


3.02 


2.87 


2.71 


25 


2.74 


2.56 


2.40 


2.24 


2.09 


1.95 


1.82 


30 


2.10 


1.93 


1.78 


1.64 


1.50 


1.38 


1.26 


40 


1.32 


1.18 


1.05 


0.93 


0.83 


0.73 


0.64 


50 


0.88 


0.76 


0.65 


0.56 


0.42 


0.40 


0.34 



14 STEAM POWER PLANTS 

Table 2 gives the rate of depreciation that should be charged 
for various periods of life of apparatus at various rates of interest 
return upon the sinking fund. For instance, if the assumed life is 
20 years and the interest return on the sinking fund is 5 per cent, 
3.02 per cent of the initial cost of the apparatus would be the 
annual depreciation. 

Cost of Power-plant Equipment. — The author has been urged 
to furnish data as to the cost of power-plant apparatus, and 
has reached the conclusion, after an attempt to do so, that 
such information as might be given would be misleading and 
therefore had better be omitted, as the cost varies so with the 
quality and size of apparatus purchased, the location of the plan, 
and conditions governing its installation. It is far preferable 
for an engineer to obtain actual estimates of the various kinds of 
apparatus under consideration, and then all uncertainty will be 
eliminated. It is equally difficult to give costs of labor for power- 
plant operation. 



CHAPTERS II. 

PROPORTIONING STEAM BOILERS. 

Heating Surface Necessary. — The function of a steam boiler 
is to transmit to the water it contains as much of the heat gener- 
ated by the combustion of fuel as possible. Each square foot of 
heating surface in the boiler can transmit only a certain amount 
of heat when the highest economy is being realized. By in- 
creasing the supply of heat a greater amount is transmitted and 
consequently a greater amount of water is evaporated by each 
square foot of heating surface; but with the increase, the same 
percentage of the heat generated is not utilized. The reason is 
that, after a certain, rate of evaporation is reached, the maximum 
capacity of the water to absorb heat is more nearly reached, and, 
hence, a larger percentage of the heat of the fuel passes up the 
chimney. In other words, it is possible to evaporate a certain 
amount, say 3 pounds, of water per square foot of heating sur- 
face in a given time and to utilize a certain percentage, say 80 
per cent, of the heat in the fuel, 20 per cent going to waste. 
It is also possible to burn more coal and evaporate say 5 pounds 
of water per square foot of heating surface in the same time, but 
when doing so a greater percentage, perhaps 25 per cent, of the 
heat of the fuel is lost. The selection of the proper amount of 
heating surface for a steam boiler is, therefore, a very important 
matter. 

The best efficiency, under ordinary working conditions, with 
most boilers, is obtained when evaporating about 3 pounds of 
water per square foot of heating surface per hour, from a feed 
temperature of 212° F. into steam at atmospheric pressure. 
This is equivalent to allowing nearly 12 square feet of heating 
surface per boiler horse-power. Most water-tube boilers are 
rated upon the basis of 10 square feet of heating surface per 
horse-power. Most boilers, sometimes, and quite frequently in 
fact, attain a very high efficiency when the rate of evaporation 
is considerably higher than that given. Such high results are 

15 



16 STEAM POWER PLANTS 

usually attained, however, when all of the many conditions 
affecting the efficiency are such as to produce a good result. 
Many of these conditions are not so favorable when a boiler is 
operated in ordinary service. For instance, if the boiler surfaces 
are not clean, owing perhaps to the accumulation of scale or 
soot, the efficiency of the heating surface will be more or less 
impaired. For this and other reasons, the writer believes it is 
well, at least in plants where the load is fairly uniform, to provide 
ample heating surface for the work to be done; for not only will 
such a course result in a saving of fuel at ordinary rates of 
evaporation, but it will make it possible to run a boiler consider- 
ably above its rating and still maintain a high efficiency. With 
electric generating stations or other situations where the maxi- 
mum load is of short duration, so liberal an allowance of boiler 
capacity is not good practice ; for some types of water-tube boilers 
can be driven at double the rating if there is sufficient draft to 
burn the necessary coal on the grates; and this can be done, too, 
without seriously affecting the efficiency. For this reason the 
saving in first cost may, in instances of this kind, more than 
offset the decreased economy due to driving the boilers above 
the normal rating for the short period of heavy load. Dr. D. S. 
Jacobus, in the Journal of the Franklin Institute for December, 
1910, writes as follows concerning the rating of boilers in cen- 
tral-station practice: 

" Much depends on the load curve of a power plant in obtain- 
ing economy. If a continuous uniform load could be carried, 
many of the vexing problems which confront the power-plant 
engineer would be eliminated. It is difficult to .carry economi- 
cally enough reserve capacity to meet the daily peaks in the load. 
Then, again, there are exceptional peaks which occur only at 
rare intervals, so that a considerable percentage of the avail- 
able power may be developed only for a few hours every month, 
or, for that matter, for a few hours every year. Modern prac- 
tice leads more and more to developing higher ratings from 
boilers during such intervals, and a boiler should be used which, 
under proper operating conditions, may be driven to a capacity 
that is limited only by the amount of coal which can be burned 
in the furnace. Again, it is desirable to use boilers that may 
be cut into the line quickly either from banked fires or starting 
•from a cold state. 




The Engine* R:-ta REC<JHft 






Company, New York. 



j*^. »^»^=^^^f^tfi^^ ; ,^^^^wfld^ — ^L^-^ ffr^c^-^-T^^ i^- — ^p- 



5tcnr,Tay. 



Mkmst5\SRl 




Plate 2. —Ninety-Sixth Street Power Station, Metropolitan Street Railway Company, New York. 
m. g. siarrett, chief engineer; f. s. peerson, consulting engineer. 



STEAM POWER PLANTS 17 

" The practice in this respect is exemplified by considering 
the installations of the Commonwealth Edison Company at 
Chicago, where the first 5000-kw. turbines erected in this coun- 
try were installed. This was in 1903, and eight boilers each hav- 
ing about 5000 square feet of heating surface were supplied for 
running a turbine. The maximum rating for these turbines was 
7500 kw. Later on 12,000-kw. maximum-rating turbines were 
installed, each with eight boilers of the same size as provided 
for the 5000-kw. machines. Still later machines of 14,000 kw. 
maximum were run with the same size and number of boilers as 
the original machines of 7500 kw. maximum." 

Value of a Boiler Horse-power. — According to the American 
Society of Mechanical Engineers' standard, a boiler to develop 
1 horse-power must raise 30 pounds of water per hour from a 
temperature of 100° F. to the temperature of steam at 70 pounds 
pressure, and evaporate it into steam at the pressure. This is 
equivalent to evaporating 34| pounds of water per hour at a 
temperature of 212 degrees into steam at atmospheric pressure, or 
" from and at 212 degrees," as it is sometimes called. The term 
horse-power is frequently used when estimating the capacity of 
steam boilers, and the custom of buyers was formerly to ask for 
boilers of a certain horse-power. This is an improper way to buy 
boilers unless the amount of heating surface per horse-power is 
closely examined. If bids are called for boilers of a given horse- 
power, one bidder might offer a boiler with ample heating surface, 
while another might offer a boiler with much less. Both might 
develop the required horse-power, but the one with deficient heat- 
ing surface might do it only at an increased cost for fuel, as 
explained in a previous paragraph. In saying this it should be 
borne in mind that the efficiency of various classes of surfaces 
varies according to their location and arrangement, but this 
variation in first-class boilers is confined to narrow limits which 
can only be detected by the expert. 

Advantages of Types of Boilers. — Barrus, in his excellent work 
on " Boiler Tests," states that " the economy with which different 
types of boilers operate depends more upon their proportions and 
the conditions under which they work than upon their types; 
and, moreover, that when these proportions are suitably carried 
out and when the conditions are favorable, the different types of 
boilers give substantially the same result." So much for the side 



18 



STEAM POWER PLANTS 



of efficiency. As to safety, the water-tube boiler is generally 
considered to be far superior to boilers of the fire-tube type. 
While water-tube boilers seldom explode, although the tubes 
sometimes burst and injure those firing them, it is not believed 
that water-tube boilers as a class are immune from series ex- 
plosions. Some types, however, have never experienced such a 
disaster. Water-tube boilers also possess an advantage in that 




\"°lron 




4" Channel? 



8"Brick 
Pizr. 



35'l 



44- 



Boiler Room Floor. 



Fig. 4. Iron Walk over Boilers designed by Sheaff & Jaasted. 



they contain less water than the shell type, as usually designed, 
and consequently steam can be raised in them more quickly. 
More water can probably be evaporated per square foot of 
heating surface in a water-tube boiler than in one having fire 
tubes, on account of a larger and longer passage for the gases, 
and possibly on account of a better circulation of water in contact 
with the heating surfaces. The efficiency of the two types is 
about the same, the difference depending more upon the propor- 
tions and management, as Mr. Barrus states, than upon the types. 



- 



^*x?» Sfrair. 



^ts-\<^ Strainer. ■>, ' ' r i r-—^ 



a [^i ,3"Su ction. w 




Plate 3. — Tower Station, Hartford and Springfield Street Railway Company, 
e. h. kitfield, engineer. 



STEAM POWER PLANTS 19 

Water-tube boilers have increased in favor very rapidly in the 
past few years, particularly for electric work, where large amounts 
of steam are wanted suddenly, and sometimes without previous 
warning. In spite of the fact that the water-tube boiler pos- 
sesses advantages over it, the fire-tube boiler, particularly the 
horizontal return tubular boiler, is still used to a very consider- 
able extent on account of its lower cost. An internally fired 
boiler, such as the Manning, locomotive, Galloway, or Lancashire 
boiler, all of which are of the fire-tube type, possesses advantages 
over the brick-set boilers in that there is not the air leakage into 
the furnaces, reducing the efficiency, that is often found in the 
boilers which require a brick setting. Furthermore, they do not 
need the costly brickwork. Internally fired boilers are, on the 
other hand, unless provided with large furnaces, very poorly 
adapted for burning bituminous coals, which require large com- 
bustion chambers, in order that the flame from the burning coal 
cannot come in contact with the relatively cooler surfaces of the 
boiler and thus become cooled to such an extent that combus- 
tion ceases and the gases pass to the chimney unconsumed and 
consequently wasted. For this same reason, horizontal tubular 
boilers must be raised a good deal higher above the grate if 
bituminous coal is to be burned than if anthracite is used. Inter- 
nally fired boilers are also poorly adapted to burning small sizes of 
anthracite coals, or any coals that burn at a low rate, on account 
of the restricted grate area that is found with most boilers of this 
type. It is held by some engineers that bituminous coal gives 
the best results if it is burned in a furnace entirely separate from 
the boilers, so that the radiant heat from the fires will heat the 
fire-brick lining, or checkerwork, which is sometimes introduced 
in the combustion chamber, to such an extent that the gases 
coming in contact with this highly heated brickwork are con- 
sumed before reaching the boiler. Horizontal return tubular 
boilers are seldom used for pressures as high as 150 pounds, and 
this fact has a good deal to do with the preference engineers have 
for water-tube boilers, where pressures of from 175 pounds to 
200 pounds are common, particularly with turbines. Probably 
the greatest advantages of water-tube boilers is the economy of 
space their use brings about of the large size units in which they 
may be obtained, units of 2500 horse-power being manufactured. 
Economy of space is of such vital importance in large central 



20 STEAM POWER PLANTS 

stations that water-tube boilers are invariably used in such 
plants in the United States. 

Division of Heating Surface in Units. — The first problem con- 
nected with the design of a boiler plant is to determine accurately 
the maximum number of pounds of steam that will be used by 
the various engines, pumps, and other parts of the plant which 
will have to be supplied. As has been said, 1 square foot of 
heating surface should be allowed in shell boilers for every 3 
pounds of water to be evaporated into steam from and at 212 
degrees in an hour's time. With water-tube boilers the heating 
surface can be obtained by dividing the number of pounds of 
water to be evaporated into steam from and at 212 degrees per 
hour by 3.4. With this proportion and sufficient draft and grate 
surface to burn the necessary amount of fuel, a boiler can easily 
be forced 33J per cent over this capacity and maintain a good 
efficiency. Some boilers can do much better than this. In a 
test of Babcock and Wilcox marine boilers, by the U. S. Navy 
Department, for the battleship Wyoming, the efficiency was 74.3 
per cent and 69.1 per cent with an evaporation of 3.88 pounds 
and 10.52 pounds of water per square foot of heating surface 
per hour respectively. It ought to be stated that the maximum 
evaporation of a boiler is limited mainly by the amount of coal 
which can be burned upon the grate. If the draft is sufficient, 
a good boiler can develop a horse-power upon one-half of the 
surface recommended. By dividing the total number of pounds 
of steam that are to be evaporated from and at 212 degrees per 
hour by 3 for fire-tube boilers and by 3.4 for water-tube boilers, 
the amount of heating surface for plants with a constant load 
may be obtained with sufficient accuracy. 

The next step is the subdivision of this heating surface into the 
proper number of boilers. This is of considerable importance, 
for careful study may result in much saving in the first cost and 
in the cost of operation. For instance, if boiler capacity equiva- 
lent to evaporating 28,800 pounds of water from and at 212 
degrees an hour is required, 9600 square feet of heating surface in 
fire-tube boilers will be needed. If each square foot of heating 
surface may be overloaded 33J per cent, it is evident that if 
the 9600 square feet were divided among four boilers, one boiler 
might be shut down for repairs or cleaning, which is frequently 
necessary, and the other three run at 33| per cent overload and 



STEAM POWER PLANTS 21 

still evaporate 28,800 pounds of water per hour. If the total 
heating surface was divided into three boilers, each of 3200 square 
feet of heating surface, two might not be able to run the* plant 
alone, so a fourth or spare boiler would have to be supplied. 
This would manifestly be a poor division of power, as the money 
spent on the spare boiler would represent so much capital lying 
idle most of the time. The frequency with which a boiler is shut 
down for repairs or cleaning depends upon the attention given it 
and the character of the feed water. 

Importance of Proper Grate Surfaces. — To evaporate a given 
amount of water into steam, it is necessary to generate a certain 
amount of heat by the combustion of fuel. The factors con- 
trolling the amount of heat generated are, the kind of coal, 
the amount of grate surface the boiler contains, and the draft. 
Ample grate surface, therefore, is highly desirable, particularly 
when boilers are to be forced. The draft affects the rate of com- 
bustion, as the amount of coal burned on each square foot of 
grate surface in an hour's time is usually called. Of the factors 
mentioned, that pertaining to the kind of coal to be used should 
be determined by an engineer before designing a boiler plant. 
He should investigate the cost of the various fuels available at 
the locality at which the boiler plant is to be constructed, and, 
with these data and a knowledge of the relative evaporative 
power of the different fuels, he can determine in advance the 
cheapest kind of coal, the evaporative power and cost of each 
being considered, and construct the boilers so that it can be used. 
Many plants have been seriously handicapped by the failure of 
their designer to consider this subject. Some coals, besides hav- 
ing less heating power per pound than others, cannot be burned 
at as high a rate of combustion on account of peculiar properties 
they possess. For instance, with the finer sizes of anthracite coal, 
it is impossible, unless mechanical draft is used, to burn more 
than a small amount on a grate, as the particles pack together 
so closely that the air cannot get through the bed of fuel in suffi- 
cient quantity to permit a rapid combustion. Again, a coal high 
in ash and sulphur is limited in the rate at which it can be burned. 
Of course, if only a limited amount of fuel can be burned per 
square foot of grate surface in a given time, the grate has to be 
made large in proportion to the heating surface, and, when it 
is intended to burn a low-grade fuel, provision for a large grate 



22 STEAM POWER PLANTS 

ought to be made in the first place. If a plant is designed to burn 
a low-grade fuel, and it is desired to change to a fuel of better 
grade, this can be done by reducing the size of the grate by 
bricking off a portion of it. With a better fuel less coal would 
be burned, and it would probably be burned at a higher rate; 
consequently so large a grate would not be needed. It might 
seem that it would not be necessary to reduce the size of the 
grate to burn less fuel, but, although less fuel could be burned 
per square foot of grate by reducing the draft, yet it would prob- 
ably not be good practice to do so, as it is necessary to burn 
some coals at a high rate of combustion to secure the best result. 
Too slow combustion results in the partial burning of the gases, 
and this causes a loss. If it is certain, before a plant is con- 
structed, that there never will be a desire to operate it with a 
lower grade of fuel than that for which it is designed, it would 
be foolish to provide larger grates than are necessary for this 
fuel, as boilers so constructed are frequently more expensive both 
in cost of construction and land occupied. A high rate of com- 
bustion is undoubtedly the best for many coals, for the reason 
that the gases are much more thoroughly consumed when the 
furnace temperature is high. 

Proportioning Grate. — The ratio of the grate to heating sur- 
face varies with the kind of coal and the amount burned, as was 
explained in an earlier paragraph. From a knowledge of the 
number of pounds of water to be evaporated, and the amount one 
pound of a given kind of coal will evaporate under ordinary con- 
ditions, the quantity of coal which must be burned in a given 
time can be calculated. If one knows the number of pounds of 
coal that must be burned, and the amount of coal that should be 
burned on each square foot of grate surface, in a given time for 
the normal rate of evaporation, the amount of grate surface can 
be determined. 

It remains, then, to provide sufficient draft, either by a fan or 
chimney, to produce not only the proper rate of combustion for 
ordinary demands, but also a higher one which will enable the 
boiler to operate with such overload as may be thought necessary. 
The relative evaporative power of the better grades of a number 
of different coals is shown in the table, Pocahontas coal being 
placed at 100. These figures are approximate and should be used 
with some caution. The relative evaporation for the different 



STEAM POWER PLANTS 



23 



coals shows what might be expected from the better grades of 
each kind of coal mentioned when fired by a good fireman under 
ordinary everyday conditions. The variation from these figures 
which might result from a difference in the quality of the coal 
from the same mine would be greatest with the Western coals, 
less with the Pennsylvania bituminous, and least with the semi- 
bituminous group. The anthracite, particularly the small sizes, 
might vary considerably on account of an abnormal amount of 
impurities present in the coal. The figures given in the table can 
be exceeded when all the conditions are favorable. 

TABLE 3. — RELATIVE VALUE OF STEAM COALS. 



Kind of coal. 



Pocahontas, W. Va.* 

Youghiogheny, Pa.f 

Hocking Valley, O.j 

Big Muddy, Ill.f 

Mt. Olive," Ill.f 

Lackawanna, Pa., J pea 

Lackawanna, Pa.,i Xo. 1 buckwheat 
Lackawanna, Pa., J rice 



c3 > 
0) o 



> gag 

^ ° o-~ 
Sg tjO 

~ as 5 



O— S.~ -•"* 



100 
91. 

80 

80 

67. 

84 

79 

74 



9.5 
8.7 
7.6 
7.6 
6.4 
8.0 
7.5 
7.0 



5n © 


C BO 






O IB 




a - 


5.0 




M 


C w 


M 




3.2 


c 




B-S 


ca . 






a> a> 


— o 

o o . 




-3 u - 


Is H- 2 




o © 


C 3 - 
1 ^ fc 


"3 "2 ^ 




g c o 


t. C =~ 


~ &H 


o -s. a 


Q « O 


PJ St 


15 


.3 


45 


17 


.3 


48 


18 


.3 


45 


20 


.3 


50 


20 


.3 


45 


15 


.5 


35 


13 


.6 


32 


12 


1.0 


30 



Semibituminous. t Bituminous, i Anthracite. 



Table 3 also shows about the amount of coal which should 
be burned per square foot of grate per hour under ordinary con- 
ditions; also, the ratio of heating to grate surface necessary for 
the boiler to develop its rated capacity when burning about the 
amount of coal stated and when each pound of coal is evaporating 
the quantities of water given in the table. Some authorities of 
considerable experience with Illinois coals advise higher rates of 
combustion than are recommended in the table for the best re- 
sults. A grate proportioned in accordance with the data given can 
easily be reduced in size if found desirable. It is proposed to pro- 
vide sufficient draft between the furnace and ash pit, that shown 
in the fourth column in the table, to run easily a boiler propor- 



24 STEAM POWER PLANTS 

tioned according to the data given in the table at one-third over 
its rating. For the buckwheat and smaller sizes of anthracite 
mechanical draft should be used. 

It is undoubtedly true that a better result will be obtained by 
higher rates of combustion than those given in the table, but if 
these are increased for the normal working of a boiler it will be 
necessary to have available a very intense draft, nothing less per- 
haps than that created by a high chimney or a fan, in order that 
there may be sufficient reserve draft to operate the boiler at much 
of an overload. In other words, if the rates of combustion are 
taken higher than those given for ordinary service, the draft must 
be made correspondingly greater to provide a reserve capacity in 
evaporative power. The high rates of combustion possible with 
mechanical draft are conducive to high furnace efficiency, but 
that is a subject which will be discussed later. 

Coal. — In an earlier paragraph attention was called to the 
necessity of proportioning boilers to burn the fuel which will be 
the cheapest. It seems well, therefore, to show in a general way 
some of the properties and the relative values of different steam 
coals. Such information can be misleading on account of the 
variations that exist not only in different coals, but in coal mined 
from the same seam. Nevertheless an approximate relation can 
be given for the better grades of several different coals that are 
typical of the kinds most used. What the poorer grades of coal 
of some of these kinds will do, it is impossible to predict. The 
steam coals used in the eastern and middle parts of the United 
States may be divided into anthracite, bituminous, and semi- 
bituminous classes. A coal is classified in these groups according 
to the relative proportions of fixed carbon and volatile hydro- 
carbons that it contains. The hydrocarbons are those gases 
given off by certain coals when they are heated moderately. 
Semibituminous coals contain less than 25 per cent hydrocar- 
bons and bituminous coals 25 to 60 per cent. ■ The former are the 
best steam coals for the reason that when the hydrocarbons are 
more than 20 per cent of the fuel composition, the heat value of 
the fuel becomes less, for then the hydrocarbons contain more 
or less oxygen, while with less than 20 per cent hydrocarbon the 
volatile gases are mostly hydrogen, and the coal therefore has a 
higher heat value. The percentage of hydrocarbons in anthra- 
cite coal is very small. 



STEAM POWER PLANTS 25 

Semibituminous Coals. — This group contains the finest 
steam coals mined in the United States. They are found mainly 
in Virginia, West Virginia, and Maryland. The ash varies from 3 
to 8 per cent, while the coals contain about 14,500 heat units per 
pound. The coals of this group are much more uniform in heat- 
ing power and evaporation than those of any other, but there is 
a variation in some of them, owing to the fact that care is not 
taken to exclude impurities which affect their heat value. This 
group of coals includes the Pocahontas, New River, Cumberland 
(George's Creek), and Clearfield varieties. The value is about 
in the order named, Pocahontas and New River probably being 
the most constant in quality. Placing the evaporative power of 
Pocahontas and New River at 100, none of the other coals would 
be hardly less than 95. 

Bituminous Coals. — These are found in Pennsylvania, Ohio, 
Kentucky, Tennessee, Indiana, Illinois, Missouri, and other states. 
They differ widely in heating power, not only one coal from 
another, but a great difference is also found in coal from the 
same mine. The bituminous coals are divided into two classes, 
caking and noncaking. The Indiana, Illinois, and Missouri coals 
are of the caking variety, which on burning becomes pasty and 
forms into lumps that greatly impede the fire unless broken up. 
Certain Western coals have to be burned at a comparatively high 
rate of combustion, about 20 pounds of coal per square foot of 
grate per hour, otherwise it is difficult to keep the fire from going 
out. The Pennsylvania coals are much the best for steam pur- 
poses, and the Ohio coals are usually better than those found 
farther west. 

Anthracite Coal. — This is mined chiefly in Pennsylvania, al- 
though quite a little is found in the Far West. It is principally 
composed of pure carbon, and its heat value is dependent mainly 
on the amount of earthy matter mixed with it when sold. The 
percentage of earthy matter is naturally greater in the smaller 
sizes. Anthracite coal is classified according to size into lump, 
broken, egg, stove, chestnut, pea, numbers 1 and 2 buckwheat, 
rice, and barley. Pea coal is about as large as is usually used for 
steam purposes. The larger sizes of this coal, that is, the chest- 
nut size and over, are about equivalent in evaporating power to 
Pittsburgh bituminous coal. The smaller sizes require a very 
strong draft because the particles of coal, being small, pack to- 



26 STEAM POWER PLANTS 

gether so that the air cannot get through the bed of fuel to cause 
rapid combustion. It is therefore impossible with natural draft 
to burn more than a very limited amount per square foot of grate, 
and it is inconvenient and costly to provide boilers with a suffi- 
cient grate to burn buckwheat or the smaller sizes with the draft 
due to an ordinary chimney. It is necessary, therefore, if this 
grade of fuel is to be used, to construct a 150-foot, preferably 
200-foot chimney, or to employ mechanical draft. Rice and the 
smaller sizes cannot be burned without mechanical draft. 



CHAPTER III. 

DESIGN OF HORIZONTAL RETURN TUBULAR BOILERS 
AND BOILER SPECIFICATIONS. 

The horizontal return tubular boiler is used to a far greater ex- 
tent than any other type in the United States at the present time, 
and it is intended in this chapter to give some general rules for 
designing boilers of this type. Another well-known boiler of the 
fire-tube type is the Manning, which is a vertical boiler with 
unusually long tubes rising from a high combustion chamber sur- 
rounded by water. It has been used successfully to a consider- 
able extent in New England. Various boilers of the fire- tube 
type of special design have been illustrated from time to time in 
technical papers, but the use of these boilers is so limited com- 
pared to the horizontal return tubular boilers that they will not 
be further alluded to. A sectional view of a typical setting for a 
horizontal return tubular boiler is given in Fig. 5. The method of 
proportioning the different parts of a boiler of this type follows : 

Thickness of Shell. — One of the most satisfactory rules for 
determining the thickness of shell necessary in boilers of the fire- 
tube type is that used by the steam-boiler inspection department 
of the City of Philadelphia. The rule is as follows: 

Working pressure = 2 Tts -5- Df, 

in which 

T = the ultimate tensile strength of the plate in pounds per 

square inch; 
t = the thickness of the plate in inches; 
s = the efficiency of the longitudinal joint; 
D = the diameter of the boiler in inches; 
/ = the factor of safety. 

The factor of safety is usually taken at 5. With a tensile 
strength of 60,000 pounds and a joint efficiency of 80 per cent, 
the rule shows that with a ^-inch plate, which is about as thick 

27 



28 



STEAM POWER PLANTS 




o 

PQ 



'-4-H 

o 

bfi 

.5 
'■+3 

O 

w 

o 

'a 



bC 








O 

PQ 



o3 
Ph 

© 

§■ 



o 

bb 



STEAM POWER PLANTS 



29 



as is commonly used for the shell of an externally fired boiler on 
account of the resistance that a thicker plate offers to the transfer 
of heat at the girth seams of the boiler, the highest working 
pressure that can be carried in a boiler 6 feet in diameter is 150 
pounds. A few horizontal return tubular boiler plants have been 
designed to carry a steam pressure of 150 pounds, but it is better 
to use water-tube or internally fired fire-tube boilers if this or 
a higher pressure is to be carried unless the boilers are designed 
by an expert. 

Braces. — Braces are used in horizontal tubular boilers to 
balance the pressure exerted on those parts of the heads of the 
boiler above and below the tubes and not close to the shell. If 
these parts are not braced, the pressure would cause the flat head 
to bulge outward. For a distance of 3 inches from the shell, and 
for a distance of 2 inches from the tubes, the head is usually con- 
sidered to be sufficiently stiffened by the circumferential joint and 
the tubes not to need other bracing. Fig. 6 shows one of the 
heads in a horizontal tubular boiler, and the part which has to be 
braced is indicated. Braces used in this work are usually of two 
kinds, — the direct or through stay or brace, which extends entirely 




Fig. 8. Connecting Direct Braces. 



through the boiler and joins the heads together, and the diagonal 
or crowfoot brace. This latter is shown in Fig. 7. The head 
is connected to the adjacent shell by it. The diagonal brace is 
preferred by the boiler-inspection companies, as it is much easier 
to get inside of a boiler to inspect the interior with this brace than 
with the direct type. If the latter are used they should be suffi- 
ciently separated to allow a man entering the manhole opening to 
pass between them. The braces should be distributed uniformly 
over the area they are intended to support. Fig. 5 shows the 
manner in which diagonal braces may be distributed over the 
head. Five direct braces are sometimes used, three being placed 
in a lower row and two above, all being symmetrically placed with 



30 



STEAM POWER PLANTS 



reference to the center. When direct braces are used the heads 
are frequently further stiffened by channel iron or angle irons 
riveted to the heads as shown in Fig. 8. If manholes are placed 
in one of the heads of the boiler, the heads below the tubes should 
be braced. 

In determining the number and size of braces, the area in square 
inches of the surface to be stayed rnoist be calculated and then 
the total pressure on this area. This latter divided by 7500 will 
give the cross-sectional area in square inches that must be pro- 
vided in all of the braces combined, 7500 pounds per square inch 
being the greatest strain to which a brace should be subjected. 
Cutting a thread on the end of the braces for the nuts reduces 
the area of metal somewhat, and this should be taken into account. 
Sometimes the ends of the braces are upset, that is, heated and 
hammered at the end so that their diameter is increased slightly 
where the thread is to be cut. 

With diagonal braces the pull exerted is not perpendicular to 
the head of the boiler; hence the area of the brace should be 




Method of Suspending Boiler. 



calculated by dividing the surface supported by 7500 and then 
increasing the result by multiplying the quotient obtained by the 
length in inches of the brace divided by the distance in inches 
that the head is from the point where the brace is attached to the 
shell. Referring to Fig. 7, the length of the brace is the dis- 
tance A B, and the distance from the head to the point where the 
brace is attached is the distance C B. The ratio A B : C B is 
the amount that the brace should be increased. For instance, if 
the surface to be stayed should require the pull of a brace 1 square 
inch and the length A B should be 48 inches and the length C B 
40 inches, then the area of brace actually required would be 
1 X 48 -f- 40 = 6 -r- 5 = l\ square inches. 



STEAM POWER PLANTS 



31 



Supporting Boilers. — For many years the practice has been to 
support boilers by riveting two pairs of lugs on the sides of the 
shell, as in Fig. 6, and supporting them on cast-iron plates built 
into the setting, rollers being placed under the pair of lugs in the 
rear, so that the movement due to expansion will be toward the 
rear. The principal objection to this plan is that the settlement 
of the walls of the setting, which is almost sure to occur, often 
throws almost the entire work of supporting the boiler on two 
lugs. A number of engineers suspend a boiler by riveting straps 
to the shell and passing hooked rods through them and through 
cast-iron plates resting on I beams laid across the top of the setting. 
Fig. 9 shows this construction. This is one of the best methods. 
If it is used it is well to have an iron plate of generous size be- 
tween the beams and the setting for the former to rest upon. 



TABLE 4. 



TUBE SPACING AND HEATING SURFACE IN HORI- 
ZONTAL TUBULAR BOILERS. 



Diam- 
eter 
boiler, 
inches. 


Tubes. 


Heating 

surface 

per 

linear 
foot of 
boiler, 
square 

feet. 


Size of man- 
holes, 
inches. 


Tubes, center 
to center. 


Center 
of boiler 
to cen- 
ter of 
upper 
row 
tubes, 
inches. 


Usual length 

of boiler, 

feet. 


Diam- 
eter, 
inches. 


Num- 
ber. 


Internal 

area, 

square 

feet. 


Hori- 
zontal, 

inches. 


Verti- 
cal, 

inches. 


A. 


B. 








D. 


"' E. 


F. 


G. 




48 


3 


46 


1.94 


43.67 


9X14| 


4i 


4 


6^ 


10 to 12 


50 


3 


52 


2.19 


48.69 


9X14| 


4| 


4 


6f 


10 to 12 


52 


3 


54 


2.28 


50.58 


9X14i 


4J 


4 


71 


10 to 12 


54 


3 


60 


2.53 


55.60 


9X14| 


4| 


4 


n 


10 to 12 


56 


3 


64 


2.70 


59.06 


11X15 


4i 


4 


8 


10 to 12 


58 


3 


70 


2.95 


64.09 


11X15 


4A 
*2 


4 


8i 


10 to 12 


60 


3 


76 


3.21 


69.11 


11X15 


4i 

^2 


4 


8^ 


10 to 12 


48 


3| 


34 


1.97 


38.68 


9X14| 


5 


41 
^2 


6| 


12 to 14 


50 


3^ 


38 


2.20 


42.66 


9X14i 


5 


41 


61 


12 to 14 


52 


3| 


46 


2.67 


50.31 


9X14| 


5 


4i 


7| 


12 to 14 


54 


3| 


47 


2. '73 


51.53 


9X14^ 


5 


4| 


71 


12 to 14 


56 


31 


50 


2.90 


54.60 


11X15 


5 


4 1 
^2 


7\ 


12 to 14 


58 


3| 


52 


3.02 


56.74 


11X15 


5£ 


^2 


7f 


12 to 14 


60 


3* 


56 


3.25 


60.71 


11X15 


5i 


4-i 
^2 


8f 


14 to 16 


62 


31 


60 


3.48 


64.72 


11X15 


5| 


^2 


81 


14 to 16 


64 


3^ 


64 


3.71 


68.67 


11X15 


5£ 


4i 
^2 


9 


14 to 16 


66 


3| 


70 


4.06 


74.49 


11X15 


5| 


4i 
^2 


9| 


14 to 16 


54 


4 


36 


2.75 


46.17 


11X15 


6 


5 


7 


16 to 20 


56 


4 


38 


2.90 


48.59 


11X15 


6 


5 


7| 


16 to 20 


58 


4 


40 


3.05 


50.99 


11X15 


6 


5 


7^ 
• 4 


16 to 20 


60 


4 


47 


3.59 


58.63 


11X15 


6 


5 


8 


16 to 20 


62 


4 


49 


3.74 


61.04 


11X15 


6 


5 


8| 


16 to 20 


64 


4 


51 


3.89 


63.45 


11X15 


6 


5 


8f 


16 to 20 


66 


4 


56 


4.27 


69.00 


11X15 


6 


5 


9 


16 to 20 


68 


4 


62 


4.73 


75.59 


11X15 


6 


5 


9§ 


16 to 20 


70 


4 


64 


4.88 


78.01 


11X15 


6 


5 


9f 


16 to 20 


1 72 


4 


74 


5.65 


88.79 


11X15 


6 


5 


10i 


16 to 20 



32 



STEAM POWER PLANTS 



Tubes. —7 Tubes should not be so closely spaced in a boiler as 
to interfere with a proper circulation of water in them. Three 
3§- and 4-inch tubes are commonly used in horizontal tubular boil- 
ers, the last being generally used in large-size boilers, the size 
decreasing with the diameter of the boiler. Barrus states that a 
certain ratio of tube area to grate surface is necessary to give the 
best result with different fuels, a ratio of nine to one or ten to 
one being proper for anthracite coals and six to one or seven to 
one for bituminous coals, the difference being due to the large 
volume of gases with bituminous coals, which requires a large 
area in the tubes to pass the gases at the proper velocity for 
giving off their heat. Tubes should be placed in vertical rows 
and not staggered. They should be located as far apart as the 
number necessary to put in the boiler will permit; for this will 
permit a better circulation, which is essential when the boiler is 
operating at high rates of combustion. 





Fig. 10. 



Fig. 11. 




Fig. 12. 




if— IB"— A 
H'Extra Heavy PipeMi 

Plate 4. — Boilers at Plymouth Cordage Company. 

DR. E. D. LEAVirr, ENOWEER. 



Half Section C-C ' Half Rear Elevation. 



STEAM POWER PLANTS 



33 



By means of Table 4 and Figs. 10, 11, and 12 the proper method 
of locating and spacing tubes in return tubular boilers may be 
found. The three figures refer respectively to 60-inch boilers 
with 3-, 3J- and 4-inch tubes. These data have been taken from 
Mr. W. M. Barr's work, " Boilers and Furnaces." Fig. 8 has 
also been taken from the same source. In using Table 4 to de- 
termine the number and location of tubes for boilers of different 
diameters than those shown in the figure, a drawing of the tube 
sheet should be made on which the centers of the tubes can be 
located from the data given in the tables. Barr states that " the 
distance from the side of a tube to the inside of the boiler shell 
should not, in the case of a 36-inch boiler, be less than 2 inches, 
for a 48-inch boiler it should not be less than 2J inches, and for 




1 












Icp 


1 





© 


1 


©1 


| f-C 


o l 


) ->p- E 


->f-[ 


3 S" 


C->i 




cFj 


©J 

ft* 


o 






1 1 "^ 


-o 






o 




UfH 












P^° 




o 


o 




oi| 


J £. 


-© 






o 




i! < 


o 


o 


o 


o 


1 ' 1 


'l-e- 




o 


o 




©! 


,jl . . 










, 1'. 



Fig. 13. 



a 50-inch boiler and larger, the distance should be not less than 
3 inches, to secure good water circulation." Calculations have 
been made showing the heating surface per lineal foot of boiler for 
each of the different sizes given in the table, also the usual length 
of each. The tube area is also given, and this may be useful in 
comparing the tube area with the size of grate. The method of 
determining the proper amount of heating and grate surface was 
explained in the preceding chapter. 



34 



STEAM POWER PLANTS 



TABLE 5. — DIMENSIONS OF DOUBLE-RIVETED STAGGERED 

SEAMS. 



Thickness 

of sheet, 

inches. 



J 

1 6 



Diameter 

of rivets, 

inches. 



II 

16 
3. 
4 



1 



15 
16 



Diameter 

of rivet 

holes, 

inches. 



3. 
4 

11 

16 
15 
16" 

1 



Pitch, 


Lap, 


inches. 


inches. 


9^ 

^8 


4-3- 
*16 


2* 


43 

^8 


3* 


5 


°16 


d 16 


3.32 


u 



Distance 
between 
rows of 
rivets, 
inches. 



115 
■■■16 
111 

X 16 

9-3- 

^16 

9-3- 
^16 

9-5- 



Edge of 

sheet to 

pitch line, 

inches. 



HI 
H 

119 

J-!9. 



Efficiency. 

— Weakest 

part. 



0.739 
0.717 
0.711 

0.687 
0.677 



Single-riveted Girth Seams Used with Above Longitudinal Seams. 



1 

4 
5 

16 
3 

8 

7 
16 



11 

16 

3 



15 
16 



3. 

4 
13 
16 
15 
16 

1 

1A 



9J- 

■^16 


2* 


9i 

Z 8 


■^16 


93 

Z 8 


013 
^16 


OJL. 
■^16 


3 


2 2 ^ - 


3-3- 

°16 



0.545 

0.494 

0.49 

0.466 

0.449 



TABLE 6. — TRIPLE-RIVETED LAP JOINT. 



Thickness 
of sheet, 
inches. 



4 
5 

16 
3. 
8 

JL 

16 

1 

2 



Diameter 

of rivets, 

inches. 



11 

16 



15 
16 



Diameter 

of rivet 

holes, 

inches. 



1 



11 

16 
3. 
4 
13 
16 
1A 
16 



Pitch, 
inches. 



3 

3| 

3| 

3f 
01 5 

^T6" 



Lap, 
inches. 



6^ 
6| 

7tf 
8| 



Distance 

between 

rows of 

rivets, 

inches. 



2 
9-1- 

•"16 

2& 
2* 

21 



Edge of 

sheet to 

pitch line, 

inches. 



H 



Efficiency. 

— Weakest 

part. 



0.77 
0.76 
0.75 
0.75 
0.746 



Single-riveted Girth Seams Used with Above Longitudinal Seams. 



1 

4 
5 

16 
3. 

8 
J_ 
16 



11 
16 

3. 

4 



15. 
16 



11 
16 
3 
4 
13 
16 
15 
16 



9-L 

■"16 


91- 

•"16 


91 


24 


91 


97 

■^16 


2| 


913 

■"T6 


2* 


3 



0.456 

0.419 

0.412 

0.42 

0.398 



STEAM POWER PLANTS 



35 



TABLE 7. — TRIPLE-RIVETED BUTT JOINT WITH DOUBLE 

WELT. 



Thick- 
ness of 
sheet, 
inches. 


Diam- 
eter of 
rivets, 
inches. 


Diam- 
eter of 
rivet 
holes, 
inches. 


Thick- 
ness of 
strap, 
inches. 


A. 


B. 


c. 


D. 


E. 


F. 


Effi- 
ciency. 
—Weak- 
est part. 


5 

16 
3 

8 
7 
16 

1 
2 


n 

16 
3 

4 

7 

8 

15 

16 


3 
4 
13 
16 
1 5 
1 6 
1 


i 

4 

5 
16 

3 

8 

7 
16 


6i 
6§ 

6f 


3£ 

3f 
3! 


2f 
2| 
2| 
3 


2±- 

9-3- 
-^16 

2| 
2f 


2 \ 
2j¥ 

013 
-^16 

3 


n 


0.88 
0.75 
0.86 
0.866 


Single-riveted Girth Seams Used with Above Longitudinal Seams. 


Thickness of 
sheet, 
inches. • 


Diameter of 
rivets, 
inches. 


Diameter of 

rivet holes, 

inches. 


Pitch, 
inches. 


Lap, 
inches. 


Efficiency. 

— Weakest 

part. 


5 

16 
3 
8 
7 

16 
1 
2 


n 

16 
3 
4 
7 
8 
15 
16 


3 

4 

13 

16 

15 
16 

1 


2 
2 

2£ 


21 

-^16 
013 

•^16 

3 


0.446 
0.438 
0.444 
0.442 



Riveting. — In Tables 5, 6, and 7 there are given proportions 
of riveted joints recommended by the Hartford Steam Boiler 
Inspection and Insurance Company, which are published through 
the courtesy of that corporation. The efficiencies for the dif- 
ferent joints, given in the table, are to be substituted in the 
formula for determining the thickness of shell plates. The dimen- 
sions to which the letters in Table 7 refer are shown in Fig. 13. 
Butt joints are far superior to lap joints, as there is not the 
tendency of the plate to crack on a line parallel with and near 
the rivets. The joints are designed for metal having a tensile 
strength of from 55,000 to 60,000 pounds, and the efficiency cal- 
culations are based upon the latter figure. The shearing strength 
allowed to the rivet steel per square inch of section in single 
shear, when used in steel plates, is 38,000 pounds, and a rivet 
in double shear is considered to be equivalent to 85 per cent 
additional. Rivet steel is allowed for shearing strength 45,000 
pounds per square inch of section. In the calculations for the 
efficiency the rivet is assumed to fill the hole, and the diameter 
of the rivet hole, not that of the rivet, is therefore used. The 
efficiency of the girth seams given in the tables need not be con- 
sidered in determining the thickness of shells of boilers. 



36 STEAM POWER PLANTS 

Boiler Settings. — Fig. 5 shows a longitudinal and cross sec- 
tion of popular form of setting for return tubular boilers. It 
should be constructed of hard red brick, laid in lime or cement 
mortar, and the entire setting ought to be lined with fire brick, 
with every fifth course laid as headers, so that any part that might 
become damaged could be easily renewed without taking out the 
entire lining. Sometimes, to economize, the furnace as far as the 
bridge wall only is lined with fire brick. The fire brick should 
be laid in fire clay, using as little of it as possible. In the draw- 
ing the grate has a width equal to the diameter of the boilers, and 
the side wall is battered so as to leave a space of 3 inches at the 
level where the setting closes into the boilers. The side walls are 
provided with air spaces, as shown, which are necessary to pre- 
vent the wall from cracking. 

If fire brick backed with common brick is used, the side walls 
have to be 13 inches thick, and the air space should be about 
2 inches wide at the bottom and diminish as its sides converge. 
Two 13-inch walls and a 2-inch air space make the entire thick- 
ness of the wall between the boilers 28 inches. This diminishes 
at the top as shown. It is sometimes difficult with low-grade fuels 
and natural draft to burn sufficient coal on the grate of a hori- 
zontal tubular boiler to obtain as high evaporation as might be 
needed, hence it is desirable, if these boilers are apt to be fired 
with such fuel, to place the boilers a little farther apart and make 
the side walls perpendicular and at a distance apart at the grate 
equal to the diameter of the boiler plus 6 inches. This makes 
the grate 6 inches wider and increases its surface materially. If 
a boiler is constructed in this way, it is a simple matter to dimin- 
ish the size of the grate by bricking off the sides and rear. It is 
difficult to fire a grate more than 7 feet deep, although they are 
sometimes made 9 feet in depth, in large boilers. Furnaces over 
5 feet wide should have two fire- and two ash-pit doors. 

The top of the bridge wall of the boiler is usually about 10 or 
12 inches from the bottom of the shell, and the space behind may 
be filled with earth and paved with common brick or left empty. 
Curving this combustion chamber to conform with the shell only 
reduces its size, which is a disadvantage with bituminous coal 
and of no use with other kinds. The rear wall should contain 
an air space and be provided with a clean-out door about 16 
by 20 inches. The wall should be located at a distance of 18 



STEAM POWER PLANTS 37 

to 24 inches, depending on the size of the boiler, from the back 
head. 

The back connection, that is, the connection between the rear 
wall and the head, is a source of more or less trouble on account 
of the expansion and contraction of the boiler, and the difficulty 
of making a joint that will remain tight. One method is to spring 
an arch across, having one end resting on the wall and the other 
upon an angle iron riveted to the back head of the boiler. The 
arch consists of brick resting in an iron framework. The Hart- 
ford Steam Boiler Inspection and Insurance Company uses an 
arch somewhat similar to that shown in Fig. 5. 

The grate should be at a level of 24 inches above the floor and 
the shell from 28 to 30 inches above the grate with anthracite coals 
and from 36 to 42 inches if bituminous coals are to be burned, 
as the gases from the latter do not burn properly if the flame 
comes in contact with the cooler boiler surfaces. The floor of the 
ash pit should be paved with brick laid on edge and flushed with a 
thin cement mortar so as to be water-tight. This floor is usually 
3 to 6 inches below the floor of the boiler room. 

An interesting horizontal tubular boiler is shown in Plate 4 and 
Fig. 14. This boiler was built for a steam pressure of 185 pounds 
per square inch from the plans and specifications of Dr. E. D. 
Leavitt, consulting engineer. A full description of it appeared 
in the Engineering Record of May 18, 1901. 

Boiler Specifications. — It was thought advisable to print one 
or two typical specifications for horizontal return tubular boilers 
and to outline a method to be pursued in purchasing water-tube 
boilers, the difference in construction of boilers of the latter type 
making it necessary for the specification to be mainly a general 
description of what is wanted and what the boilers are to do. 

In the first form of specification printed, which calls for the 
delivery and setting of a boiler, those clauses that relate to the 
prosecution of the work, the removal of rubbage after its com- 
pletion, remuneration for a change in the plans, interpretation of 
drawings, etc., are omitted. The specification is divided into 
sections, and in some cases comment or explanation follows a 
section. A form of specification for high-grade work follows: 

Intent of Specifications. — It is the intent and purpose of these specifica- 
tions to provide for the furnishing and installation of a complete boiler plant 
comprising the boilers, setting, grates, fronts, feed and blow-off piping, gauges, 



38 



STEAM POWER PLANTS 



smoke breeching, flues, dampers, and such details as are hereinafter specified, 
all complete and erected ready to generate steam. 




-%,' 



|«- 2^4 



4 W-JrSjS 



% 



fe". 



1 



I7 y n 



Section of Shell 
at Joint. 



Enlarged Sec+ion of Head and Shell. 



-"A," 



93" 



f^"*--- 8'7V 36 Equal Spaces, 2.864" Pitch 

- '-^»" Ri ve ts . — . ' 



o 
o o 



e-l 



-e- 



o.| 



ro 

§|mt3 ^Po9 



o o 
o 



■o. 



e-c 



^ 



Mie=-__i 



Longitudinal Joints Rear Course. 




Hanse 



Manhole Cover and Yokes 



Section B-B. 



Fig. 14. Details of Leavitt Boiler. 



Materials. — The shells and heads of the boiler are to be constructed of 
open-hearth steel having a tensile strength of from 55,000 to 65,000 pounds 
per square inch, with a yield point not less than one-half the tensile strength 
and an elongation of 25 per cent in 8 inches. (See note below.) Test 
specimens cut from the plates must, when cold, be capable of being bent 
180 degrees flat on themselves without fracture on the outer side of the bent 
portion, also, after being heated to a light cherry red and quenched in water 
of a temperature between 80° and 90° F. For the bending tests the test speci- 
mens shall be \\ inches wide, if possible, and for all material f inch or less 
in thickness, the test specimen shall be of the same thickness as that of the 
finished material from which it is cut; but for material more than f inch thick, 
the bending specimen may be only \ inch thick. One specimen for the cold 
bending and one for the quenched test to be furnished from each plate and 



STEAM POWER PLANTS 



39 



marked for identification. Specimens for the tensile tests of the dimensions 
shown in the upper illustration in Fig. 15 are to be cut from each plate, marked 
for identification, and given to the engineer. 

Rivet steel shall have a tensile strength of from 45,000 to 55,000 pounds 
per square inch, the yield point to be not less than one-half the tensile strength 
and the elongation 28 per cent in 8 inches. Rivet steel of the full size as 
rolled shall pass the same bending tests as specified for shell plates. Two 
tensile test specimens shall be furnished from each melt of rivet rounds. In 



riCT ^ not less than 9' L 228.60fhm 






il 



«3fc 

"^Ts 7ft 



¥ 



12.70 
mm, 



i 



Wl 



33$ 



\^25.40mm fp^ j 
IQ"-457.20mm Abfi- *j 



[^ -— 4'^" -10195mm A 

f^O^-kk"^ 2k'S7 15mm ^V-mtg^ 




k i 

S.35fr?m. 




■%•*- 2"-50.80mmk %4 
%.*?\nm. ^9.5^mm. 

Fig. 15. Dimensions of Test Specimens. 



case any one of these develops flaws or breaks outside of the middle third of 
its gauged length, it may be discarded and another test specimen substituted 
therefor. Two cold bending specimens and two quenched bending specimens 
shall be furnished from each melt of rivet rounds. 

Note. — The foregoing section upon materials is an abstract of the stand- 
ard specification for boiler plate and rivet steel adopted June 29, 1901, by 
the American Section of the International Association for Testing Materials. 
Reference to the chemical properties of the steel has been omitted. A varia- 
tion in the elongation with different thicknesses of plate is provided as follows: 
For each increase of \ inch in thickness above f inch, a deduction of one per 
cent shall be made from the specified elongation. For each decrease of ys inch 
in thickness below £■ inch a deduction of 2\ per cent shall be made in the 
specified elongation. 

Shell and Heads. — The shell plates are to be — inches thick, the heads — 
inches thick. The shell is to be in three courses (or two courses if the boiler 
is small enough), and the middle one must be of the smallest diameter. The 



40 STEAM POWER PLANTS 

edges of the plates must be planed before they are put together and calking 
must be done with a round-nosed tool. Heads must be flanged to a radius 
not less than 1| inches and they must be annealed after flanging. The flange 
must be free from cracks and flaws. 

Riveting. — The girth seams are to be of the single-riveted lap-joint type, 
the pitch of the rivets to be — inches, lap — inches, and rivets — inches in 
diameter. The longitudinal seams are to be placed well above the fire line 
and to be of the butt type triple riveted with double welt, as shown in the 
drawing (which the engineer should supply). The rivet holes are to be 
drilled or punched | inch small and afterward drilled or reamed out to full 
size. A reamer must be used instead of the drift-pin. The bur is to be 
removed and the rivets driven by a hydraulic or pneumatic riveter as far as 
possible. 

Note. — Some specifications intended for high-grade work demand that 
the rivet holes shall be punched £ inch small and the shell then rolled and the 
lapping ends bolted together while the holes are drilled out the full size. This 
insures that the holes in one end of the sheet shall come opposite those in the 
other end, and much better riveting will be the result. Oftentimes the holes 
are punched out to the full size, but authorities unite in saying that the metal 
immediately surrounding a punched hole is weakened. Hence it is better to 
punch the holes small and drill or ream them out to full size. 

Bracing. — The heads are to be braced to the shell by — radial solid crow- 
foot braces, — on each head distributed as shown on drawing. The braces 
must be of — inch stay-bolt iron at least 3 feet long, forged up without a weld 
and be connected to the shell by two — inch rivets. Each brace must be so 
located as to lie in a plane passing through the axis of the boiler. 

Note. — If through braces are used, their number and diameter should 
be given and their location shown on a drawing. If the ends of the braces 
are to be upset, or if channel or angle irons are to be riveted to the heads to 
stiffen them, it should be so stated, and their weight and dimensions specified, 
or shown by a drawing. 

Tubes. — The tubes are to be — in number, — inches in diameter, — feet 
long, of the best charcoal iron lap welded or of steel. The tube holes in the 
head are to be chamfered and the tubes are to be carefully expanded and beaded 
over at the ends. The tubes are to be located as shown in a drawing (which 
the engineer should supply). 

Manholes. — A pressed steel manhole frame, 11 by 15 inches, is to be 
riveted to the top of each boiler, with the long diameter girthwise (in a posi- 
tion indicated by the engineer), and another is to be riveted to the front head 
below the tubes. The usual pressed steel manhole plate, gasket, yoke, and 
bolt are to be provided for each. 

Handhole. — A 4-by-6-inch handhole is to be placed in the back head 
below the tubes. The plate, gasket, yoke, and bolt are to be provided. 

Nozzles. — Each boiler is to have two — inch cast-iron nozzles riveted to 
the boiler in the middle of the front and rear courses. The nozzles are to be 
drilled to fit the A. S. M. E. standard flange schedule. 

Lugs. — The boiler is to be supported on the brickwork by four heavy 
cast-iron lugs riveted to the shell, one pair to the front and the other to the 



(Bott o m of Hoof T russ. 




Plate 5. — Power Station at Navy Yard, Brooklyn, N. Y. 

REAR-ADMIRAL GEORGE W. MELVILLE, CHIEF ENCINEER. 



STEAM POWER PLANTS 41 

rear course. The front lugs shall rest upon bearing plates. Three 1-inch 
rollers shall be placed under each rear lug between it and the bearing plates, 
which are also to. be provided. 

Note. — If the boiler is to be supported by straps from beams laid across 
the top of the setting, it should be specified and a drawing showing the detail 
of the method of hanging the boiler given. 

Feed Pipe. — The contractor is to supply and connect a — inch steel (or 
brass) feed pipe that is to pass through a brass bushing in the front head of 
each boiler, at one side and 3 inches above the tubes and extending to the rear 
of the boiler. 

Tools. — Each boiler is to be provided with a fire shovel, slice bar, hoe, and 
poker. The boilers are to be provided with one tube scraper and the necessary 
hose and nozzle for blowing soot from the interior of the tubes. 

Blow-off. — A blow-off connection is to be provided at the bottom of each 
shell at the back end. The — inch opening in the shell is to be tapped to 
receive a — inch blow-off pipe and the opening is to be reenforced by a — inch 
steel plate riveted to the shell. The blow-off pipe is to be protected by a 
fire-clay tube and run in the manner shown in the drawing to a blow-off main 
provided for in another contract. The boiler contractor is to supply a — inch 
blow-off cock of — make for each boiler and the fire-clay tube for protecting 
the blow-off pipe. 

Castings. — Each boiler is to be provided with a cast-iron flush front, 
cheek plates, mouth plates, one (or two) fire and one (or two) ash-pit doors 
and clean-out door for rear wall, arch plates, grate bars, bearing bars, T bars 
for back connection, tie rods, wall braces, etc. The grate bars shall contain 
50 per cent air space and are to fit a grate — by — inches and to be suitable 

for burning coal. The fire doors are to be fitted with registers and 

perforated linings, the ash-pit doors with registers, and the clean-out door with 
a lining. 

Fittings. — Each boiler to be furnished with the following fittings, which 
are to be connected: One water column upon which can be mounted a steam 
gauge, gauge cocks, and gauge glass connected to the boiler by l|-inch pipe; 
three — inch gauge cocks ; one — inch gauge glass ; one — inch steam gauge 
of — make and provided with stopcock and siphon. 

Hydrostatic Test. — The boiler must be made sufficiently tight to stand 
without leaking when subjected to a hydrostatic test of a pressure 33 \ per cent 
in excess of the normal working pressure of — pounds. 

Setting. — The boilers are to be set in accordance with the accompanying 
drawing. The settings are to extend 6 inches below the floor level and are 
to be of the best brick laid in lime mortar and the entire setting is to be lined 
with the best quality of fire brick laid in fire clay and with every fifth course 
set as headers. The setting is to be closed in at the shell 5 inches above the 
center line of the boilers, except at the lugs where the setting closes in two 
courses below the lugs. The boilers are to be supported by lugs as previously 
stated, and care must be taken that bearing plates are placed level and 
that rollers under the rear and middle lugs are placed perpendicular to the 
axis of the boilers. The foundations for the setting are to be laid by the 
contractor. 



42 



STEAM POWER PLANTS 



Smoke Flue and Chimney. — If an iron chimney is to be used, 
some believe, in small work, that it is best to put the boilers, 
smoke breechings and flue, damper and damper regulator, and 
chimney in the boiler contract, for the reason that all of them 
affect the operation of the boiler. The method of proportioning 
the chimney, etc., is discussed later. The boiler specification, 
therefore, should indicate the thickness and dimensions of the 
smoke flue. Provisions should be made for a damper in the up- 
take of each boiler that may be closed when the boiler is under- 
going repairs. There should be a damper in the main flue, and 
this should be under the control of an automatic damper regu- 
lator which opens or closes the damper according as the steam 
pressure is respectively below or above the normal. The smoke 
flue should have doors through which the soot may be removed 
when necessary. 



~^~ 1& "^TorofWc 



Top of lA /gtef^G/as s. 

V-->i '^"^ 



:iU>Rods 

•eoccco 
iil cccoco 

TOOOOOOOOO 

.IP 

JOOOOOOO 



offom of Wwe&Ju, Glass. 

ooooo 

ooooo 

O<30000000 
QQQ 



x oc 



J OOCCOOOCIOCOOOOCO i 

\\\l oooooooo oooooooo 

JL OOCCCCCOiOCOOOCCO j 

Km. ooooooo poooooo // 

COOCCO COOOOO' 



GOO. 



,000 



■5"Tlbes. 



Fig. 16. 



The following specification for a horizontal return tubular 
boiler, without the setting, was prepared by Messrs. Dean & 
Main, a well-known firm of mill engineers, and it is printed 
through their courtesy. The author believes it to be an excellent 
specification for the purpose intended. It will be noticed that 
it calls for the construction and delivery of the boilers only. 
Appended to the specification was a blue-print, reproduced in 
Fig. 16. 



STEAM POWER PLANTS 43 

Specifications for Three 7S-inch Horizontal Return Tubular Boilers 

for 

Proposals. — Proposals will be received by Dean & Main, Exchange Build- 
ing, Boston, Mass., for building and delivering three horizontal return tubular 
boilers of the following general dimensions : 

Working pressure by gauge, lbs 125 

Inside diameter of end rings of shell, in 78 

Thickness of shell, in xk 

Length of tubes, ft 18 

Diameter of tubes, in 3 

Number of tubes 166 

Width of grate, ft 7 

Length of grate, ft 7 

Height of center of boilers above floor, ft 8. 25 

Distance from c. to c. of boilers, ft 9 

Height front of grate above floor, ft 2.5 

Height back of grate above floor, ft 2 

Thickness of heads, in \ 

Diameter of rivets, in 1 

Heating surface, sq. ft 2376 

Grate area, sq. ft 49 

Contract Price. — The price is to be stated to cover the manufacture of the 
boilers and their delivery with the accessories furnished on cars. 

Quality of Materials and Workmanship. — It is the intention that the 
materials and workmanship of the boilers shall be of the best. A repre- 
sentative of Dean & Main is to have the privilege of inspecting the boilers 
during their construction. 

Plates. — The plates are to be of the best quality of open hearth acid or 
basic steel, having the following qualities: 

Elastic limit per sq. in., not less than 30,000 lbs. 

Ultimate strength per sq. in 52,000 to 60,000 lbs. 

Elongation in 8 inches, not less than 27 per cent. 

Sulphur, not to exceed 0.35 per cent. 

Phosphorus, not to exceed 0.30 per cent. 

The plates are to be free from laminations and surface defects, and also 
to stand cold and quench bending tests flat down without showing a sign of 
fracture. The tests are to be made by (name of testing laboratory) at the 
expense of the purchaser. 

Joints. — The circular joints are to be single riveted and lapped. The 
longitudinal joints are to be butted and provided with inside and outside 
covering plates. The inside and outside covering plates are to be double 
riveted each side of the center of the joint, and the inside plate will be ex- 
tended sufficiently beyond the outside on both sides of the joint to receive 
on each side two additional rows of rivets passing through it and the boiler 
shell. Thus there will be eight rows of rivets in each longitudinal joint. 
The outer rows of rivets will have double and triple the pitches of the other 
rows. 



44 STEAM POWER PLANTS 

There will be one longitudinal joint in each plate. The boiler is to be 
made of three plates, and the joints of the two end plates will be above the 
water line on one side of the boiler and that of the center plate above the water 
line on the other side. If practicable it is preferred to have the seam near 
the bridge wall back of that wall, thus making the front plate wider than the 
others. The heads will be single riveted to the shell. 

Riveting and Holes for Rivets. — The holes for rivets will be punched one- 
fourth inch small and drilled to size with all plates and covering plates in 
place. The riveting is to be done by a hydraulic machine. As little hand 
riveting as possible is to be done. The plates are to be fitted metal to metal 
before riveting, brought up to butt in contact, and are to be properly curved 
out to the ends. No filling pieces are to be used and no drifting is to be done. 

Calking. — Calking is to be done with a round-nose tool. 

Tubes. — The tubes are to be of lap-welded steel, and are to be beaded over 
the ends. A Prosser expander is to be used. The tube holes are to be rounded 
on each side to ys mcn radius, and not beveled as is customary. The tubes 
are to be located as shown on the inclosed blue-print. (Fig. 16.) 

Manholes and Handholes. — There are to be two manholes in each boiler, 
one on top and the other in the front head below the tubes. The manhole 
on top is to be at one end of the boiler just far enough from the head to enable 
a man to get in feet first in either direction. This is to have a pressed steel 
frame, plate, and yoke. The frame is to amply make up the area of plate cut 
from the shell and is to be double riveted thereto. The manhole in the head 
is to be located as shown on the accompanying print, is to be pressed on the 
plate, and to have a pressed steel plate and yoke. There will be a 4-inch-by- 
6-inch handhole in the back head. 

Bracing. — Above the tubes there will be four longitudinal tie rods passing 
through the heads and upset at the ends, having a nut outside and inside the 
plates. There will be four braces from the heads to the shell riveted to the 
latter some 5 or 6 feet from the heads. These braces will be pinned to hori- 
zontal stiffening angles riveted to the heads. There will also be horizontal 
stiffening angles riveted to the heads above and below the longitudinal tie 
rods. Below the tubes the heads will be stiffened by several short diagonal 
braces riveted to heads and shell. 

Steam Nozzle. — There will be one 7-inch steam nozzle midway between 
the heads of each boiler. It will be a steel casting double riveted to the shell, 
and drilled for l|-inch bolts. 

Steam Box and Dry Pipe. — Bolted up against the under side of the steam 
nozzle, or screwed into it, there is to be a 5-by-5-by-7-inch tee. Into each 
5-inch branch there is to be a 5-inch wrought-iron pipe, the lengths to be equal 
and determined by the distance from the steam nozzle to the manhole nozzle. 
The top of the pipe is to be about 1 inch below the shell, and each branch 
is to be perforated on top with twenty-five 1-inch holes. The outer ends of 
the pipes are to be capped and the pipes strapped up to the shell. There are 
to be two j-inch drain holes in the bottom of the steam box. 

Safety-valve Nozzle. — There will be no safety-valve nozzle. 

Feed-pipe Nozzle and Feed Pipe. — This will be on top of the boiler near 
the front head. The feed pipe will pass through it, branch to one side and 



STEAM POWER PLANTS 45 

pass to the other end of the boiler, where it will discharge. The feed pipe will 
be 2-inch brass, iron size, and will be furnished with the boiler. 

Blow-off Pipe. — This will be tapped into the bottom of the boiler, and 
will be 2| inches in diameter. 

Safety Plug. — This will be screwed into the back head in the custom- 
ary position. A Lunkenheimer plug filled with pure Banca tin is to be 
used. 

Smoke Box. — The smoke box will not be formed by the extension of the 
main shell but by bolting a f-inch plate thereto, and having a smoke nozzle 
riveted to it. The size of the smoke nozzle will be 18 inches by 5 feet 6 inches. 
The smoke boxes will overhang. The smoke-box head will be of cast iron 
secured to the shell air-tight. The doors will likewise be of cast iron fitting 
against planed faces and having turned hinge pins and drilled holes. The 
doors are to be clamped to the head after locomotive practice. 

Damper. — A damper with two plates with a rod between them is to be 
provided with a weighted lever and chain for its control. 

Front. — The front is to be made of steel plate | inch thick. 

Grates. — These will be furnished by the purchaser. 

Fire and Other Doors. — Each boiler will have two large-size fire doors, 
with door frames, planed to match each other, and to have turned pins and 
drilled holes. The back cleaning door is to be clamped to the frame, after 
locomotive practice, to have planed joints, turned pins and drilled holes for 
pins. It will be so made that it can be securely built in. 

Supports. — The boilers will have a double set of supporting brackets at 
each end, eight for each boiler, the back ones having rolls. 

Fittings. — The contractor will furnish, but not attach, the following 
fittings for each boiler: 

One 10-inch company's steam gauge graduated to 300 pounds, and 

numbered every 20 pounds. 

One 5-inch company's safety valve set to blow at 127 pounds. 

One Reliance water column without safety device, and provided with two 
water-glass fixture bosses on opposite sides at such distances apart as will 
accommodate an 8-inch exposed length of glass. There will be no gauge- 
cock bosses. 

Two company's heavy-pattern water-glass fixtures with best Scotch 

glasses, 8-inch exposed length. 

Four extra glasses of proper length. 

Extra-strong iron-size brass piping for water column, all cut to length and 
threaded, and holes drilled and tapped therefor in shell. 

No gauge cocks will be used. 

Arch Bars. — Proper arch bars are to be supplied with each boiler. 

Buck Stays and Rods. — These are to be furnished and the buck stays are 
to be of 8-inch I beams. 

Drawing. — The party receiving the contract is to furnish a first-class 
drawing of the boiler as built, and of the setting therefor. 

Testing. — Each boiler will be tested at the works of the contractor to 
190 pounds per square inch with water pressure and made tight under that 
pressure in the presence of a representative of Dean & Main. 



46 



STEAM POWER PLANTS 



Inspection. — The boilers will be built under the inspection of Dean & Main 
and the Mutual Boiler Insurance Company. 

Reservation. — The right is reserved to reject any or all bids. 

Terms of Payment. — Proposals are to state the desired terms of payment. 

Delivery. — The proposal is to state the guaranteed time of delivery of the 
three boilers. 

Specifications for Water-tube Boilers. — An engineer's speci- 
fication for water-tube boilers can only be a very general state- 
ment of what is wanted, for the reason that such boilers vary 
greatly in design. The engineer can, however, describe what he 
wants and ask each bidder to supply information enabling him to 
understand thoroughly what each bidder proposes to furnish. 




Fig. 17. Boiler Room, Plymouth Cordage Company. 



The engineer should state in his specification the number of 
boilers he wishes to purchase, the amount of heating and grate 
surface each is to contain, the location of the plant for which they 
are wanted, and the name of the owner or owners of the plant. 
If the boilers are to be erected and placed in running order by 



STEAM POWER PLANTS 47 

the builder, it should be so stated. The engineer should state the 
kind of coal to be burned, the kind of service to be required of the 
boilers, and the dimensions of the chimney and flues. It is well 
to furnish a sketch showing the location of the boilers, flues, and 
chimney. If a mechanical stoker is to be used, the boilermaker 
should be asked to furnish a boiler setting to suit. The engineer 
should require each bidder to furnish detail drawings showing 
all parts of the boiler and setting, in such a way as to show the 
facilities for cleaning and inspecting the parts and the manner 
of making renewals. He should ask for the physical qualities of 
the metals used; the material of which the tubes are made; the 
name of the manufacturer of the different fittings used, such 
as the safety valve, blow-off cocks, water and steam gauges; the 
character of feed piping, whether iron or brass. 

For certain types of water-tube boilers with straight tubes 
slightly inclined from the horizontal and connecting with vertical 
or nearly vertical headers at the front and rear of the boilers, the 
headers connecting with combined steam and water drums, there 
are usually several different arrangements of tubes that will meet 
a specification calling for a certain heating surface. For instance, 
there may be eighty 18-foot tubes so arranged that there are eight 
tubes in width and ten tubes in height, or there may be ten 
tubes wide and eight tubes high. The latter arrangement would 
mean a wider boiler costing more, but giving a wider and conse- 
quently larger grate that might be needed with low-grade fuels. 
It is probable, the heating and grate surface and coal burned 
being the same, that a high narrow boiler of this type will give a 
better efficiency than a low wide one. If the boilermaker is to 
supply and erect the breechings, smoke flues, chimney dampers, 
and damper regulator, it should be stated in the specifications. 
If the engineer proportions the boiler, it is hardly fair to exact a 
guarantee from the maker as to the efficiency of the boiler. He 
should, however, guarantee that the boiler will operate at 50 per 
cent over its rated capacity without showing signs of deprecia- 
tion. 



CHAPTER IV. 

THE SELECTION OF THE TYPES OF ENGINES, DI- 
MENSIONS OF CYLINDERS, SPEED, STEAM 
PRESSURE, ETC. 

The method of buying a steam engine most frequently em- 
ployed by engineers is to invite bids from a number of builders 
upon an engine which, with a certain number of revolutions, 
steam pressure and back pressure, will develop a given horse- 
power. The cylinder dimensions are usually supposed to be 
looked after sufficiently when the bidders are asked to state the 
steam consumption they will guarantee. On opening the bids 
thus obtained, it is sometimes found that some offer engines with 
smaller cylinders than others, to do the same work. The prices 
are naturally different, and it occasionally happens that the 
purchaser does not get the engine best suited to his needs, first 
cost and economy of operation both being considered. The non- 
technical factory manager, knowing nothing of engines, frequently 
makes a mistake in this matter of purchasing an engine, as he does 
not know the type of engine he wants and much less what its 
details should be. He, therefore, frequently buys something very 
different from what he needs. Such an individual should either 
engage a competent consulting engineer to invite bids for him 
on the type of engine best suited to the conditions, or go to 
one reputable engine builder, inform him of the conditions that 
exist, and have an engine built to suit them. There is no doubt 
that there are builders fully competent to study the conditions 
involved and advise an owner what is required. Two or more 
builders should not, however, be placed in competition where the 
cheapest bid is likely to be the deciding factor in the selection of 
an engine, and an incompetent person is to be the judge of the 
propositions offered. It could hardly be possible to educate the 
nontechnical purchaser of engines, but there are a number of 
engineers who are not steam-engineering experts that have to buy 
engines without the aid of expert advice; and it is hoped to give 

48 



STEAM POWER PLANTS 



49 



some general information and data to assist such in determining 
the type of engine, approximate cylinder dimensions, etc., best 
suited for different situations, so that bids can be invited upon a 
specific machine and thus secure the benefit of a competition, 
where all bids are made upon the same basis. In doing this, the 
selection of the type of engine will first be discussed; afterward, 
the determination of those factors that fix the capacity and effi- 
ciency of an engine; and finally, the method of applying these 
factors in the general equation for determining the power of an 
engine so that the cylinder sizes or volumes may be calculated. 

Selection of Type. — To most people it is manifest that it would 
be bad engineering to install a costly triple-expansion engine that 
operates with the highest economy in a plant where fuel is of 
little or no value. Many situations, however, require the keenest 
judgment to select the type of engine best adapted for the service 
the engine is to perform. There is a saying that any expenditure 
for plant is warranted that results in savings which more than pay 
the interest on the expenditure, the depreciation, and the cost of 
repairs on the plant. This is a simple proposition in itself, but 

TABLE 8. — STEAM CONSUMPTION OF DIFFERENT TYPES OF 

ENGINES. 



Type of engine. 


Pounds of 

steam per 

horse-power 

per hour. 


Steam pres- 
sure, pounds 
gauge. 


High-speed simple 

High-speed compound noncondensing. . 


32 

24-26 

19-21 

26 

21 

20-22 

14-15 

13 


80-100 
150-110 
150-110 
80-100 
80-100 
150-110 
150-125 
150- 


High-speed compound condensing 


Corliss simple noncondensing 


Corliss simple condensing 


Corliss compound noncondensing 


Corliss compound condensing 


Triple-expansion condensing 





it is not always easy to predict the saving that will follow the 
installation of a machine, or what the depreciation and repairs 
will be. As a basis for such calculations regarding steam engines, 
Table 8 is given, and in it is shown the steam consumption per 
horse-power per hour which might be expected from various types 
of engines with different steam pressures. The figures given are 
believed to be fairly accurate in a relative sense and are supposed 



50 STEAM POWER PLANTS 

to represent about what would be obtained with each engine 
running at its most economical load, with valves and pistons in 
good but not the best condition. In the figures given for con- 
densing engines, the steam used by the air pump is included. To 
arrive at the actual cost of power, the fuel cost and the cost of 
repairs, interest, depreciation, etc., should be taken into account. 
It can be safely assumed that with good anthracite or semibitu- 
minous coal a boiler will evaporate 8 pounds of water per pound 
of coal; hence the annual fuel cost of an engine will be: 

Annual fuel cost = P X H.P. X h X c -5- (8 X 2240), 
in which, 

P = the pounds of steam used by the engine per horse-power 
per hour; 
H.P. = the average horse-power developed; 

h = the number of hours during the year the power is being 

used; 
c = the cost of coal in dollars per ton of 2240 pounds. 

To the annual fuel cost thus obtained there should be added, 
say 4 per cent of the cost of the engine, to cover the interest on 
the investment and 8 per cent for repairs, depreciation, etc. It 
is assumed that, when the formula is used to compare condens- 
ing engines with simple engines, the boiler feed water in the case 
of the condensing plant is first warmed by the exhaust steam 
from the engine and afterward by the steam from the auxiliaries, 
so that there will not be enough difference in the temperature of 
the feed water in the two cases to warrant taking this difference 
into account. 

No really reliable figures as to the cost of engines can be given, 
as this is constantly varying, due to the condition of supply and 
demand and the cost of materials. If an engineer is in doubt as to 
the type of engine needed for a special situation, bids on the types 
that are to be considered should be obtained, and from the prices 
thus obtained a decision can be made. The increased cost of the 
most economical engines is partly offset by the fact that not so 
great a capacity in boilers is required to run them, hence the cost 
of the boilers should usually be considered. Generally speaking, 
it has been found that the greater expense of economically work- 
ing engines is more than offset by the gain resulting from their 
use. For all steam pressure over 100 pounds with engines over 150 



STEAM POWER PLANTS 51 

horse-power, the compound engine in most situations, whether it 
is to be operated condensing or noncondensing, will save enough 
in fuel cost to pay for its increased first cost and cost of attend- 
ance, repairs, etc. There are situations where this statement 
would not be true; for instance, when the fuel cost is exceptionally 
low or when the demand for exhaust steam for heating or for man- 
ufacturing purposes is in excess of the steam exhausted by the 
engines. It would then, it is manifest, be poor policy to buy an 
expensive engine for the sake of getting an economical one, when 
the economical use of steam in the engine is no object. Again, 
if an engine is only to be run occasionally, as in the case of a relay 
engine to a water wheel, the engine should not be as costly a one 
as if it were to run more frequently. In the latter case, the in- 
terest on the increased cost of an economical engine over one using 
more fuel might be more than the difference in the fuel cost, owing 
to the short time that the engine is used. If an engine runs a 
large part of the time only partially loaded, as it would in driving 
an electrical generator for street railway plants or for electric ele- 
vators where the load is widely fluctuating, it is doubtful if com- 
pound engines would pay. Generally speaking, triple-expansion 
engines for mill or electric work with steam pressures as low as 
150 pounds have not shown that the saving due to their use is 
sufficient to pay for their increased cost over a compound engine. 
Engines used in the power plants of very large buildings should, 
generally speaking, be of the compound type, if over 200 horse- 
power. They are naturally run noncondensing. Another point 
to be considered is the increased cost of attendants for the most 
economical engines over those with simpler parts and using more 
fuel. 

Steam Pressure. — The steam pressure employed in simple 
engines may be said, generally speaking, to vary from 80 to 120 
pounds above the atmosphere, and in compounds from 100 to 150 
pounds, although the latter are sometimes run with lower pres- 
sures than 100 pounds. The tendency is toward the higher pres- 
sures. High-pressure steam, especially in compound engines, is 
conducive to high economy, but it should not be forgotten that 
high steam pressures, and by that is meant pressures of 135 pounds 
and over, mean increased wear on the system, much trouble with 
steam piping if unusual care is not taken in constructing it, and 
an increased loss from leakage and condensation ; but for all these 



52 STEAM POWER PLANTS 

objections the higher economy of engines with high steam pres- 
sures will more than compensate for the drawbacks if the plant 
is well designed and is placed in competent hands. In electric 
power stations and with mill and factory engines of large power, 
the pressure can well be from 135 to 150 pounds. In very large 
central stations pressures of 175 pounds are common. High- 
pressure steam is of special importance where compound non- 
condensing engines are used. For plants for very large build- 
ings employing competent engine attendants, a pressure of at 
least 120 pounds should be selected if this type of engine is to 
be used; and in large mills or large electric plants, where the 
steam plants will be in competent hands, the steam pressure with 
noncondensing compound engines should be as high as 150 
pounds. Even with pressures as high as 125 pounds the steam 
piping should have unusual attention both in the design and 
erection. 

Rotative Speed. — The number of revolutions an engine is to 
run is frequently fixed by the fact that it is to be directly con- 
nected to a dynamo which has to be run at a certain speed, or 
by some other condition. The rotative speed is limited by the 
centrifugal force developed in flywheels when in motion, by 
the maximum speed at which the piston should be run, and, in 
the case of engines with a releasing valve gear, such as the Cor- 
liss, by the tendency of the valve gear to become noisy and 
give trouble at too high a speed. High-speed engines of 10-inch 
stroke, with automatic cut-off controlled by a shaft governor, are 
usually run at about 325 revolutions per minute, and the rotary 
speed is decreased to about 150 revolutions in engines of 24 
inches stroke. An engine may be run at much lower rotative 
speeds than those mentioned, but it would then, of course, 
require a proportionally larger cylinder to develop the same 
power, other conditions being equal. With releasing-gear engines 
with ordinary air dashpots, the highest rotative speed that should 
be employed seems to be about 100 revolutions per minute. In 
electric work the rotative speed is sometimes increased above 100 
revolutions per minute for engines directly connected to a dy- 
namo, but unless some special valve gear is used, permitting high 
speeds, the life of the engine is shortened and it is apt to be noisy 
and require considerable attention. The rotative speed of an 
engine is frequently limited by the proper speed at which the 



STEAM POWER PLANTS 53 

piston should be run. The need of a high rotative speed for 
electric work is due to the fact that the higher the speed the less 
is the cost of an electric generator. In electric work the rotative 
speed of an engine is determined by the speed of the generator to 
which it is to be connected, and the speed of an engine for this 
service should not be fixed until information as to the speeds of 
standard generators is obtained. 

Piston Speed. — Piston speed is usually defined as being the 
number of feet that the piston of an engine travels in a minute's 
time. It is obtained by multiplying the length of the stroke in 
feet by twice the number of revolutions per minute. Good prac- 
tice with high-speed engines limits the piston speed of small 
engines with a length of stroke of 12 inches to about 550 feet 
per minute, and with engines with a 2-foot stroke to about 600 
feet. In larger engines 700 feet per minute is allowable, and 
in electric service this figure is sometimes exceeded in long- 
stroke engines to obtain a high rotative speed. It is not well 
to go above 800 feet, however, for, when this piston speed is 
exceeded, very large ports are necessary to admit the larger 
amount of steam required with high piston speeds, and these 
large ports increase the clearance of the engine and make it less 
economical in the use of steam. 

Mean Effective Pressure. — When steam is admitted to a cyl- 
inder during a portion of the stroke of an engine and then further 
supply is "cut off," the steam, after "cut-off " occurs, begins to 
expand as the piston advances and consequently the pressure 
falls. The work done in the cylinder is proportional to the aver- 
age effective pressure throughout the stroke, hence it is necessary 
in proportioning cylinders to know what this average or mean 
effective pressure should be with different steam pressures. The 
mean effective pressure is one of the factors in the general equa- 
tion for determining the horse-power developed by an engine. Its 
selection is an important matter, for on it, more, perhaps, than 
on anything else, the economy of the engine is dependent. Theo- 
retically, the greatest amount of work is obtained from steam 
when it is admitted to a cylinder up to such a point in the stroke 
that it will afterward expand to the pressure that the engine is 
exhausting against. Practically, it is not well to have so complete 
an expansion. The more complete the expansion is (that is, the 
number of times the volume of steam at cut-off is expanded), 



54 



STEAM POWER PLANTS 




Fig. 18. Power Plant, Lancaster Mills, Clinton, Mass. 
(Lockwood, Greene <& Co., Engineers.) 



STEAM POWER PLANTS 5b 

the less the mean forward pressure must be, hence engines operat- 
ing with high economy work, up to a certain limit, with a lower 
mean effective pressure than a similar engine working with a 
poorer economy. The lower the mean effective pressure is, how- 
ever, the larger the cylinder must be to accomplish the same 
work, hence the expansion may be so great and the mean effective 
pressure so small that the saving in fuel due to this complete 
expansion may not pay for the increased cost of the large cylin- 
der. This is, in brief, the commercial problem involved in the 
selection of cylinder sizes. 

Mean Effective Pressures for Simple Engines. — In Table 9 
there are given the approximate mean effective pressures that are 
usually obtained with various steam pressures with Corliss and 



TABLE 9. — MEAN EFFECTIVE PRESSURES FOR DIFFERENT 
STEAM PRESSURES, IN POUNDS PER SQUARE INCH, FOR 
ENGINES OF THE SIMPLE TYPE. 



Steam pressure, gauge 

Corliss,* condensing 

Corliss,* noncondensing 

Single-valve, noncondensing. 



80 
26 
36 
42 



90 
28 
38 
46 



100 
30 
40 
50 



* These data can be applied to four- valve moderate- or slow-speed engines. 

other four-valve slow- or medium-speed engines, condensing and 
noncondensing, when the minimum amount of steam per horse- 
power per hour is consumed. The table also shows the same 
data for simple single- valve engines of the high-speed type. 
The overload capacities of engines proportioned in accordance 
with the figures given in the table are described in a later para- 
graph. 

Proportioning Cylinders of Single-cylinder Corliss Engines. — 
The first thing to do in determining the size of cylinder for an 
engine to develop a given horse-power is to fix the steam pres- 
sure and afterward select a mean effective pressure proper for the 
conditions under which the engine is to work. Having the above 
data, the method of determining the cylinder size will be ex- 
plained, in one case where the number of revolutions is fixed, and 
in another case where it is not. It will first be supposed that 
the number of revolutions have been fixed. 



56 STEAM POWER PLANTS 

The general equation by which the horse-power of a double- 
acting engine is determined is in the form: 

H.P. = P XlXaXn + 16,500, ... (2) 
in which 

P = the mean effective pressure in pounds per square inch; 
I = the length of stroke in feet; 
a — the mean area of the piston in square inches; 
n = the number of revolutions per minute. 

In equation (2) the terms H.P. (the number of horse-power 
to be developed) , P, and n are assumed to be known, and trans- 
posing we have 

iXa = H.P. X 16,500 -*- (P X n). . . . (3) 

Substituting the value of P, n, and H.P., we can find the 
numerical value of I X a. Both of these quantities are to be 
determined. Table 3 shows in columns 1 and 2 the diameter 
and length in inches of cylinders for Corliss engines, for which 
practically all large engine builders carry patterns. The cylinder 
sizes given are taken from the catalogue of the Allis-Chalmers 
Company. Column 3 shows the number of revolutions at which 
it is recommended these engines should run. Column 4 shows 
the product of the cylinder area in square inches by the length of 
stroke in feet for each cylinder, and column 5 shows the quan- 
tities given in column 4 multiplied by the number of revolutions 
given in column 3. Going back to the calculations, the numerical 
value oil X a, it will be remembered, has been found. We now 
look down column 4 until we find a number nearest to the numeri- 
cal value of I X a. Opposite the number thus found are the 
dimensions of the cylinder that is seemingly required. One 
more operation remains. The length of stroke of this cylinder 
in feet should be multiplied by twice the number of revolutions 
that the engine is to run to obtain the piston speed; and if this 
exceeds good practice, as described in an earlier paragraph, a 
cylinder with a shorter stroke and larger diameter, but of approxi- 
mately the same volume, can probably be found in the table, 
which will give the power without too great a piston speed. 

If the revolutions are fixed in the first place, the problem is 
simpler. We then can transpose equation (2) to 

I x a X n = H.P. X 16,500 vP, ... (4) 




X 




Plate 6. — Power Station, Union Traction Company, Anderson, Ind. 

SARGENT & LUNDY, ENGINEERS. 



STEAM POWER PLANTS 



57 



TABLE 10. — DIMENSIONS OF CYLINDERS AND SPEEDS OF 

CORLISS ENGINES. 



Diameter cyl- 


Length stroke, 


Revolutions per 


Area of cylinder 
in square inches X 
stroke in feet=ZX<z. 


Area of cylinder in 
square inches X 


inder, inches. 


inches. 


minute. 


stroke in feet X rev- 
olutions = lXaXn. 


12 


30 


90 


282 


25,447 


12 


36 


85 


339 


28,840 


14 


36 


85 


461 


39,252 


14 


42 


82 


538 


44,177 


16 


36 


82 


603 


49,461 


16 


42 


78 


703 


54,889 


18 


36 


80 


763 


61,070 


18 


42 


78 


890 


69,467 


18 


48 


75 


1,017 


76,338 


20 


42 


75 


1,099 


82,467 


20 


48 


72 


1,256 


90,478 


20 


60 


75 


1,570 


117,810 


22 


42 


75 


1,330 


99,784 


22 


48 


72 


1,520 


109,477 


22 


60 


65 


1,900 


123,542 


24 


48 


70 


1,809 


126,669 


24 


60 


65 


2,261 


147,026 


26 


48 


70 


2,123 


148,660 


26 


60 


65 


2,654 


172,552 


28 


48 


68 


2,463 


167,484 


28 


60 


65 


3,078 


200,118 


30 


48 


68 


• 2,827 


192,265 


30 


60 


62 


3,534 


219,126 


30 


72 


55 


4,241 


233,263 


32 


48 


65 


3,217 


209,105 


32 


60 


62 


4,021 


249,317 


32 


72 


55 


4,825 


265,402 


34 


48 


65 


3,631 


236,058 


34 


60 


62 


4,539 


281,455 


34 


72 


55 


5,447 


29%613 


36 


48 


72 


4,071 


293,146 


36 


60 


62 


5,089 


315,539 


36 


72 


55 


6,107 


335,897 


38 


60 


60 


5,670 


340,233 


40 


48 


70 


5,026 


351,859 


40 


60 


62 


6,283 


389,558 


40 


72 


55 


7,539 


414,691 


40 


84 


50 


8,796 


439,824 


42 


48 


70 


5,541 


387,923 


42 


60 


62 


6,927 


429,486 


42 


72 


55 


8,312 


457,196 


44 


48 


70 


6,082 


425,748 


44 


60 


62 


7,602 


471,364 


44 


72 


55 


9,123 


501,774 


46 


60 


62 


8,309 


515,189 


46 


72 


55 


9,971 


548,427 


48 


60 


62 


9,047 


560,963 


48 


72 


55 


10,857 


597,154 



58 



STEAM POWER PLANTS 



and after obtaining the numerical value of I X a X n, the proper 
diameter and stroke of cylinder and rotative speed of the engine 
required can be found opposite the number in column 5 of the 
table nearest to the numerical value of I X a X n. If there is 
not a close agreement between one of the numbers in column 5 
and the value of I X a X n, the revolutions may be increased or 
decreased as the former is respectively greater or less than the 
latter. 

It was explained that Table 10 gives the cylinder sizes of 
Corliss engines made by one company and that many builders 
carry patterns for these sizes. Most builders have additional 

TABLE 11. — DIMENSIONS OF CYLINDERS AND SPEED FOR 
HIGH-SPEED AUTOMATIC CUT-OFF ENGINES. 



Diameter cyl- 


Length stroke, 


Revolutions per 


Area of cylinder 
in square inches X 
stroke in feet=ZXa. 


Area of cylinder in 
square inches X 


inder, inches. 


inches. 


minute. 


stroke in feet X rev- 
olutions=ZXaX«. 


9 


10 


325 


53 


17,225 


10 


10 


325 


65 


21,125 


11 


10 


325 


79 


25,675 


11 


12 


300 


95 


28,500 


12 


12 


300 


113 


33,900 


13 


12 


300 


132 


39,600 


14 


12 


300 


153 


45,900 


14 


14 


275 


178 


48,950 


15 


14 


275 


205 


56,375 


16 


16 


250 


268 


67,000 


17 


16 


250 


302 


75,500 


18 


16 


250 


338 


84,500 


18 


18 


225 


381 


85,725 


20 


18 


225 


471 


105,975 


20 


20 


200 


523 


104,600 



patterns, varying more or less in size from those given, and it may 
be that for a particular case a builder might furnish a cylinder 
with slightly shorter stroke, and correspondingly greater area of 
piston, so that the cylinder volume would be the same. Such a 
cylinder would give the same power, and, because of the shorter 
stroke, the engine would be less expensive to build, the frame, 
guides, and all reciprocating parts being shorter. For this reason 
it is not well for the engineer to be too rigid in fixing the cylinder 
dimensions. Cylinders of different engines to do the same work 
should have the same volume; but the stroke should not be 
shortened too much. 



STEAM POWER PLANTS 59 

Proportioning Cylinders for Single-cylinder High-speed En- 
gines. — Table 11 contains the sizes of cylinders of a line of 
high-speed automatic engines. Although no one builder carries 
patterns for them all, most builders have patterns for cylinders 
of approximately the same volume as those given in the table. 
The engineer can determine the size cylinder required in the 
manner described for Corliss engines, using the mean effective 
pressure and rotative speed proper for this type of engine. A 
specification for this type of engine can name the length and 
diameter of cylinder wanted, but it should also state that bids 
upon engines of approximately the same cylinder volume will 
be considered. It is, of course, unfair to handicap a builder not 
possessing patterns of exactly the dimensions desired by demand- 
ing that he make a pattern to conform exactly to the engineer's 
specification. 

Proportioning Cylinders for Medium-speed Engines. — It is 
impossible to give a table that is representative of the cylinder 
sizes of medium-speed engines, as those four-valve engines which 
run at higher rotative speed than Corliss engines and at lower 
rotative speed than the so-called high-speed engines are called. 
The reason for this is that no two builders have patterns for the 
same sizes of cylinders. It is, perhaps, just as well to select 
the engine size from the catalogue of one builder, using the same 
piston speed and mean effective pressure as for Corliss engines, 
and invite bids upon an engine with a cylinder or cylinders of 
equivalent volume. The shorter stroke should belong to the 
cheaper engine, other things being equal, for reasons explained 
above. An engine with too short a stroke in proportion to its 
diameter is not as economical usually, on account of greater 
clearances. 

Proportioning Cylinders for Compound Engines. — The method 
of determining the size of cylinders of compound engines is some- 
what complicated by the fact that steam has to be expanded 
through two cylinders. Theoretically, the size of the high-pres- 
sure cylinder for a given number of expansions in the engine has 
absolutely nothing to do with the capacity of the engine. In fact, 
a simple engine, with its single cylinder the same size as the 
low-pressure cylinder of a compound engine, would, theoretically, 
develop the same power as the compound if the cut-off in the 
single cylinder were adjusted so as to give the same number of 



60 



STEAM POWER PLANTS 



expansions as exist in the compound engine. In practice, how- 
ever, the large number of expansions common in compound en- 
gines would not do in a simple engine, because of the excessive 
cylinder condensation that would occur. Dividing the expan- 
sion between two cylinders, as is done in the compound engine, 
reduces the condensation, and that is why compound engines 
are used. For the purpose of determining the cylinder sizes of 
a compound engine, it can be assumed that all of the work is 
done in the low-pressure cylinder, and then determine its size 
by the formulas given for the simple engines, assuming a mean 
effective pressure that is proper for a compound engine. After 
the size of the low-pressure cylinder is determined, the high-pres- 
sure cylinder dimensions can be found by selecting one whose 
volume is in the same ratio to the volume of the low-pressure 
cylinder, that practice has found to be proper. 

Mean Effective Pressures for Compound Engines. — The mean 
effective pressures in compound engines are different from those 
in simple engines for the reason that the steam pressures and 
ratios of expansion are higher. In Table 12 there are given 
values that can be assumed for the mean effective pressures for 

TABLE 12. — MEAN EFFECTIVE PRESSURES FOR DIFFERENT 
STEAM PRESSURES, IN POUNDS PER SQUARE INCH, FOR 
COMPOUND ENGINES. 



Steam pressure, gauge 

Corliss,* condensing 

Corliss, * noncondensing 

Single-valve, high-speed, condensing 

Single-valve, high-speed, noncondensing. . . 



100 


125 


150 


18 


20 


22 


29 


31 


33 


22 


24 


26 


32 


34 


36 



These data can be applied to four- valve moderate- or slow-speed engines. 



substitution in equations (3) and (4) to find the size of the low- 
pressure cylinder of compound engines of various types. The 
mean effective pressures given are equivalent to the mean effec- 
tive pressures actually found in the low-pressure cylinder added 
to the mean effective pressure in the high-pressure cylinder mul- 
tiplied by the ratio of high-pressure to the low-pressure piston 
areas. The mean effective pressures given for compound engines 
are believed to be such as will insure the lowest steam consump- 
tion per horse-power. Overload capacities are discussed later. 



STEAM POWER PLANTS 61 

The data given in the tables have been gathered mainly from 
an examination of a number of tests made by engineers known 
to obtain trustworthy results, where the conditions have been 
such as to obtain the highest efficiency. In all cases the mean 
effective pressure is based upon a back pressure of 16 pounds 
absolute in the case of noncondensing engines, and a vacuum 
equivalent to 26 inches of mercury in the case of condensing 
engines. After the mean effective pressure is decided on, for- 
mula (3) should be used if the revolutions are not fixed, and 
formula (4) if they are determined upon, just as was done with 
simple engines, in calculating the area and length of stroke of the 
low-pressure cylinder of a compound engine. 

After the size of the low-pressure cylinder is determined, the 
high pressure can be found by selecting one whose area is in the 
same ratio to the area of the low-pressure cylinder, as practice 
has found to be proper, as has been said. There is a difference 
of opinion among engineers as to the proper ratio of cylinder 
volumes with compound engines. Some engineers proportion the 
cylinders so that the amount of work done in each will be the 
same. This results, particularly with high pressures, in a con- 
siderably greater range of temperature in the high-pressure than 
in the low-pressure cylinder; and by many this is held to be bad 
practice, for it is well known that too great a temperature range 
results in excessive cylinder condensation, and it is to overcome 
this enemy to high economy in the steam engine that compound- 
ing is resorted to. The general practice with Corliss condensing 
engines, running with constant loads, has been to use a ratio of 
1:3, 1:3J, and 1:4 with steam pressures of 125, 135, and 150 
pounds respectively. Recently the tendency of a few engineers 
and builders has been toward a comparatively larger low-pressure 
cylinder than is given. Mr. George I. Rockwood, M. Am. Soc. 
M. E., has persistently advocated a cylinder ratio as high as 1:7 
for a steam pressure of 150 pounds; and the most economical 
compound engine ever tested, that at the Grosvenordale Mills, 
Grosvenordale, Conn., which gave a steam consumption under 
12 pounds per horse-power per hour, had a cylinder ratio of 
about that proportion. A number of other engines with similar 
cylinder ratios have shown almost as good an efficiency. With 
high-speed automatic single-valve engines the cylinder ratio 
varies from about 1:2J with 100 pounds pressure to about 1:3 



62 



STEAM POWER PLANTS 



with a pressure of 150 pounds. An advantage in having the 
high-pressure cylinder fairly large in comparison with the low- 
pressure is the greater capacity for overloads that the engine will 
then have. 

Engines with Variable Loads and Overload Capacities. — The 
mean effective pressures that are given for both simple and com- 
pound engines assume that the engines are to run with a steady 
load, and that it is desirable that they should work with the 
highest economy. In other words, the mean effective pressures 
given are such as will secure the lowest steam consumption. The 
matter of maximum economy is often of less importance in an 
engine than its maximum capacity, to take care of overloads for 
short periods. All engines are able only to work at maximum 
economy at a certain load. As the load diminishes or increases, 
the steam consumed per horse-power developed becomes greater. 
With a variable load an engine has to be large enough to supply 
the maximum power required, but when the load varies it is, 
generally speaking, better to proportion the engine so that it will 
be operating at the highest economy when working against a load 




30 
Effective 



40 &0 

Pressures. 



Fig. 19. Economy Curve, Simple Corliss Engine. 



that is something less than the maximum that it will be called 
upon to supply, for the reason that it will be working most of the 
time partly loaded, and it should be proportioned to meet this 
average load with the consumption of as little steam as possible. 
An engine should be of such a size that its most economical load, 



STEAM POWER PLANTS 63 

that is, the load under which it will operate with the least steam 
per horse-power, is equal to the average power required, provided 
the maximum power that it can develop is not less than the maxi- 
mum power that will be required. Hence, if an engine is to fur- 
nish power where the maximum demand is 400 horse-power and 
the average demand 300 horse-power, the engine required would 
be one whose most economical load was 300 horse-power, and 
300 horse-power would be the quantity substituted in the general 
equations (3) or (4) for determining the cylinder sizes. 

For the purpose of showing the variation in steam consump- 
tion due to a variation in load, the results of a number of tests, 
believed to be reliable, made upon engines of various types, 
are shown in the accompanying diagrams. Fig. 19 shows the 
result of a test by Mr. George H. Barrus upon a 16-by-42-inch 
simple noncondensing Harris-Corliss engine running 85 revo- 
lutions per minute with a steam pressure of 100 pounds. It will 
be noticed that the most economical rating on the basis of steam 
consumed per indicated horse-power per hour was when the mean 
effective pressure was about 40 pounds, increasing slightly at 47 
pounds, which was probably very near the maximum load of the 
engine. If, therefore, an engine is rated in accordance with the 
mean effective pressures given in Table 9 it is probable that 
the simple noncondensing Corliss engines, with a single eccentric 
driving both the steam inlet and the exhaust valves, would stand 
an overload of at least 25 per cent, and simple condensing Corliss 
engines over 50 per cent. 

A number of tests made upon simple high-speed engines, with 
single valves, running noncondensing, are reproduced in Fig. 20, 
and the curves there shown representing the steam consump- 
tion with the variation in the mean effective pressure are num- 
bered to correspond with the data in Table 13. Tests numbered 
1 and 2 were made by Mr. J. M. Whitham and were printed 
in the Engineering Record of July 9, 1898. Test number 4 
was made by Prof. R. C. Carpenter and was taken from Paper 
DXXIII, Transactions American Society of Mechanical Engi- 
neers. The remaining tests were made by Mr. E. J. Armstrong 
and were taken with his permission from a paper read by him 
before the Engine Builders' Association. Test number 2 was 
made upon a very small engine, but the test was not carried far 
enough to give exact data as to the proper load for it. It is 



64 STEAM POWER PLANTS 

TABLE 13. — DATA OF SIMPLE NONCONDENSING HIGH-SPEED 
ENGINE TESTS SHOWN IN FIG. 20. 



Number 
test. 


Diameter 
cylinder. 


Stroke 
cylinder. 


Revolutions per 
minute. 


Steam pressure. 


Make of engine. 


1 


13 


12 


280 


100 


Ames 


2 


8 


10 


350 


100 


Ames 


3 


13 


12 


250 


95 


Ames 


4 


12 


14 


245 


80 


McEwen 


5 


13 


12 


280 


95 


Ames 


6 


13 


12 


250 


95 


Ames 


7 


13 


12 


250 


95 


Ames 


8 


17 


16 


225 


100 


Ames 


9 


17 


16 


270 


100 


Ames 



interesting as showing the influence of size upon the steam con- 
sumption. Curves 8 and 9 were obtained from an engine of the 
same make, only considerably larger, and show a better economy 



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Fig. 20. Economy Curve, Single-valve Simple Engines. 

due, doubtless, to the larger size of engine. Curve number 4 
shows the steam consumption of an engine with a boiler pressure 
of only 80 pounds above the atmosphere. The most economical 
mean effective pressure in the latter case appears to be a little 




Floor Stand ibr Exhaust Valve 

to Condenser 
Fkx>r Stand tor Injection Valve. 

Floor Stand tor Throttle Valve 
to Air Pump. 

Floor Stand ibr Valve on feed Wafer 
Pipe to Main Heater. 

'Feed Water Pipe from Main Heater. 
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((¥&d Water Pipe 
from Separator. 



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rn, Mass. 



Fire Hose Connect* 




Feed mtcr fipe 



Plate 7. — Piping in Station, Woburn Heat, Light and Power Company, Woburn, Mass. 

SHEAFF St JAASTED, ENGINEERS. 



STEAM POWER PLANTS 65 

less than half the boiler pressure. Most of the remaining curves 
show the steam consumption of engines operating under pres- 
sures of from 95 to 100 pounds. The most economical result with 
a steam pressure of 95 to 100 pounds seems to be with a mean 
effective pressure of from 45 to 55 pounds. Generally speaking, 
therefore, with the mean effective pressures recommended in 
Table 9, the curves, with the exception of those numbered 2, 8, 
and 9, which were not carried out to the maximum capacity of 
the engine, seem to indicate that overloads of about 33J per cent 
could be met without a reduction in the speed of the engine. 
Data upon single-valve high-speed engines running condensing 
were not obtainable, as they are not often used. 

Curves 1 and 2, Fig. 21, show the variation in economy of a 
9 and 16-inch by 15-inch McEwen compound single-valve engine 
operating under a steam pressure of 112 pounds, a vacuum of 22 
inches, and a rotative speed of 265 r.p.m. One test was made 
with the cylinders steam-jacketed and one with the jackets 
shut off. The tests were made by Prof. R. C. Carpenter and 
have been taken from Volume DXXIII, Transactions of the 
American Society of Mechanical Engineers. It is seldom that 
engines of this type are provided with steam jackets, as the gen- 
eral impression seems to be that the saving does not warrant the 
expense. It will be noticed from the unjacketed test that the 
most economical rating, with a steam pressure of about 110 
pounds, seems to be with a mean effective pressure, referred 
to the low-pressure cylinder, of 26 pounds. Upon this basis it 
would seem that a compound condensing high-speed engine 
could easily run with an overload of over 50 per cent, particularly 
if the automatic cut-off be applied to both cylinders. 

Curve number 3 in Fig. 21 shows the variation in economy 
of a 12 and 20-inch by 13-inch noncondensing engine, made 
by the Ball Engine Company and tested by Messrs. George H. 
Barrus and W. S. Monroe. The average boiler pressure was 
about 166 pounds, with practically no back pressure except that 
of the atmosphere. The rotative speed was about 175 r.p.m. 
The most economical mean effective pressure seems to be about 
40 pounds compared with about 26 pounds for the unjacketed 
test of the McEwen condensing engine. While there is con- 
siderable difference in the steam pressure used by the two engines, 
it will be noticed that, if the loads were the same, the noncon- 



66 



STEAM POWER PLANTS 



densing engine would require a smaller cylinder than the con- 
densing engine, provided both were operating with the lowest 
possible steam consumption per unit of power developed. Had 
the Ball engine been rated on the basis of a mean effective pres- 
sure of 40 pounds referred to the low-pressure cylinder, the over- 
load capacity would have been about 33J per cent. The tests were 
not carried sufficiently far, however, to determine if the engine 
could be operated at greater load than that shown by the chart. 
The curve shown in Fig. 22 gives the results of tests made by 
Messrs. D. C. and W. B. Jackson upon a 700-H.P. Allis-Chalmers 
cross-compound vertical Corliss engine operated noncondensing 
and direct connected to a 500-kw. electrical generator. The 
engine has a high-pressure cylinder 24 inches and a low-pressure 
cylinder 40 inches in diameter, both with a stroke of 36 inches. 
The speed is 100 r.p.m. and the steam pressure 150 pounds 
gauge pressure. The steam consumption is based upon brake 
horse-power, so that the steam consumption per indicated horse- 
power per hour is close to 20 pounds. An exceedingly interest- 
ing feature brought out by the tests is the effect that the varying 
of the back pressure has upon the economy. 



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Fig. 21. Economy Curve, Single- valve Compound Engines. 



The compound noncondensing Corliss engine rated upon the 
mean effective pressures given in Table 5 can easily stand 25 
per cent overload if there is but a single eccentric driving the 
valve gear, and more than that if separate eccentrics are used 
to operate the steam and exhaust valves, for with two eccentrics 
a much later cut-off in the cylinder can be secured than with 
one. With compound condensing Corliss engines rated upon the 



STEAM POWER PLANTS 67 

mean effective pressures given in Table 5, overloads of at least 
50 per cent with one eccentric and probably 75 per cent with 
two eccentrics could be withstood without very greatly affecting 
the engine's speed. 

Superheated Steam, Steam Jackets, and Reheaters. — Super- 
heated steam, steam jackets inclosing the walls of steam cylinders, 
and reheating receivers placed between the cylinders of multiple- 
expansion engines are used to reduce cylinder condensation. The 
almost universal use of superheated steam on the continent of 
Europe in steam plants of recent construction and the remarkably 
high economy secured, gains from 10 to 20 per cent over the use of 
saturated steam having been reported, have drawn the attention 
of American engineers to this practice, so that the use of super- 
heated steam is increasing considerably in the United States. 
The practical objection to its use, heretofore, has been in the de- 
terioration of the superheating devices used and in the difficulty 
of lubricating engines where the steam is highly superheated. 
Recently three or four makes of superheaters have been intro- 
duced in the United States, and their extensive use abroad has 
demonstrated their durability and efficiency. The use of poppet 
valves in steam engines has overcome the difficulty of lubrication, 
although for temperatures under 500° F. these are said to be 
unnecessary. Superheaters are of two types, — those that are 
placed in the path of the gases in the boilers, or in the flue leading 
from the boiler to the chimney, and those that are heated by an 
independent furnace. Superheated steam is particularly adapted 
to steam turbines because of the increase in economy and the 
diminished wear of the turbine buckets or blades, which is greater 
with saturated steam, due, it is believed, to the erosive effect of 
the entrained moisture. 

Steam jackets are seldom used upon any engines but those of 
the slow and medium rotative-speed types, and their use becomes 
of less Value as the speed is increased. Except for slow-moving 
pumping engines their value is still a matter of doubt, although 
some engine builders provide them. Reheating receivers are in 
more common use, but their value is also a matter of dispute. 
The heating is done by a coil filled with steam of a higher pres- 
sure than that of the steam passing through the reheater. Com- 
pound- and triple-expansion engines of the slow- and medium- 
speed type are usually provided with them. 



CHAPTER V. 

SPECIFICATIONS FOR STEAM ENGINES. 

There is occasionally a tendency on the part of some to ridicule 
elaborate specifications for steam engines, yet as a specification 
is a description of what one party to a contract agrees to furnish 
to another, it should be sufficiently complete to define exactly 
what is to be supplied. A complete specification is unnecessary, 
perhaps, where an owner engages a builder, without competition, 
to construct and install an engine suited for existing conditions 
and agrees to pay for whatever the builder elects to supply. In 
competitive bidding, the builder is not legally bound to supply 
anything more than that which the specification calls for, and all 
bidders are not apt to figure on doing more than that in prepar- 
ing their bids, knowing full well that other bidders will not do 
so. Hence, if it is found, after a contract is made, that there 
are some desirable details which have been overlooked by the 
engineer in his specification, they must be purchased and paid 
for, as extras, at, naturally, a higher figure than what they 
would cost if specified in the beginning. 

The amount of detail necessary in a specification naturally 
varies with the size of the engine to be purchased and the extent 
to which the design departs from the standard types for the serv- 
ice. It is the author's intention to call attention to a number of 
details which must be considered in buying a large engine, al- 
though reference to them may be omitted in a specification for 
less important work. Some engineers believe in specifying the 
cylinder dimensions, at least in a general way, so that all bidders 
may bid upon engines of equal capacity. Methods of determin- 
ing these dimensions for simple and compound engines of various 
types were given in the preceding chapter. While they may be 
fixed by the engineer, some latitude should be given bidders in 
order that standard patterns may be utilized. In those situa- 
tions where an engineer can control the purchase of an engine, as 
they can in private work, it is safer to specify the conditions and 

68 



STEAM POWER PLANTS 69 

requirements and allow the engine builders to bid on cylinder 
dimensions of their own choosing, and this course is usually 
followed. 

A specification usually begins by stating the type of engine or 
engines wanted, whether it is to be of the simple, compound, or 
triple-expansion type, whether it is to be run condensing or non- 
condensing, and where it is to be located. Even though the en- 
gineer fixes those dimensions that determine the capacity of the 
engine, the specification should state the load at which the engine 
is to operate with the highest economy, the maximum load that it 
is to be called upon to operate, and the kind of service to which 
it is to be subjected. If guarantees as to capacity and efficiency 
are to be required from the builder, these data are, of course, 
essential. Even if they are not, and the engineer assumes the 
responsibility for the fulfillment, by the engine, of the require- 
ments imposed by existing conditions, as he does when he fixes 
the cylinder dimensions, steam pressure, and rotative speed, the 
engine builder should be informed as to what will be required of 
the engine, as he is very apt to make calculations that will serve 
as a check on those of the engineer. 

Sometimes a specification states that the price of the engine 
is to include its delivery and erection on a foundation supplied by 
the owner, and placing it in proper running condition. Again, 
however, the engine is sold free on board cars at the railway 
point nearest the locality where the engine is to be used. In the 
latter case the builder usually supplies a man to take charge of 
the erecting of the engine, which is done by labor employed by 
the owner under direction of the builder's erector. 

If the engineer has determined the cylinder dimensions, the 
rotative speed, steam pressure, and whether the engine is to be 
run condensing or noncondensing, the specification should give: 
Diameter and stroke of cylinders; number of revolutions per 
minute; horse-power to be developed when working at highest 
efficiency; horse-power at maximum load; steam pressure; back 
pressure if run noncondensing, or vacuum if run condensing. If 
the engineer does not fix the cylinder dimensions, he should give 
the rotative speed, steam pressure, and other data above men- 
tioned and ask that each bidder state the dimensions of the 
cylinder they propose to supply. 

As before stated, an engineer should not be too rigid in regard 



70 STEAM POWER PLANTS 

to cylinder dimensions, and it is well, particularly when purchas- 
ing high-speed or medium-speed engines, to state in the specifi- 
cations that engines with cylinder volumes equivalent to those 
specified will be considered. There are objections to an engine 
with too short a stroke in proportion to the area of piston; these 
were stated in the preceding chapter. If the engine is to be run 
condensing and the builder is to supply the condenser, provision 
should be made for it. 

The engineer should describe in a general way the kind of 
valve gear that is wanted. If the engine is to be of the compound 
Corliss type, the automatic cut-off might be applied to one or 
both cylinders. It is better to have it act on both cylinders if the 
load is variable, for the reason that a more equal distribution of 
the load between the cylinders will occur at light loads than there 
will if the cut-off is applied only to the high-pressure cylinder. 
Again, for Corliss engines, a separate wrist plate for the steam 
and exhaust valves, each driven by a separate eccentric, may be 
specified so that the engine may work with a later cut-off and 
consequently greater overload than is possible if both valves are 
driven from one eccentric. The cut-off may be applied to both 
cylinders in other types of compound engines. 

If the cylinders are to be steam-jacketed in barrels or heads, 
or both, it should be so stated. Consulting engineers seldom pay 
much attention to this question, as the value of steam jackets is 
still a disputed point. Generally, engines for electric service and 
factory work are not steam-jacketed, particularly if the piston 
speed is over 600 feet per minute. It is the custom in large 
multicylinder engines of the medium-speed and slow-speed 
types, to place reheating receivers in the steam pipes between the 
cylinders, in which the steam is heated in transit from one cylin- 
der to the other by live steam admitted to a coil of pipe. The 
value of these reheaters is also a matter of dispute. However, 
if they are wanted, they should be specified, also the manner in 
which the condensation that occurs in them is to be disposed of. 
The steam passing through the heater from one cylinder to the 
other is usually at a much lower pressure than the steam in the 
coils, hence the condensation must be drawn off by separate 
traps. The connection of these traps with the reheater and with 
a receptacle into which they can discharge should be made either 
by the engine builder or the steam-piping contractor. 



STEAM POWER PLANTS 



71 



If the engine is to be of the Corliss type, the kind of bed that 
is wanted should be mentioned. Two forms are made by most 
builders; one, known as the heavy-duty type, is adapted for 
heavy work and high pressures, and the other, the girder frame, 
is lighter and is of older design. The heavy-duty design is almost 



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200 400 600 800 1000 
Brake Horsepower 



1200 1400 



Fig. 22. Economy Curves, Corliss Compound Noncondensing Engine. 



invariably used for pressures over 125 pounds and to an increas- 
ing extent in lower pressures; being much stronger, it is a little 
more expensive. If bids are called for a high rotative-speed auto- 
matic engine, the specifications should call for an iron sub-base 
with the engine, for all builders do not furnish them except at 
extra expense. Occasionally the iron sub-base is not used and 
the bed of the engine is bolted to a brick foundation which is built 
up above the floor the height of the sub-base. 

There are a number of points concerning the design of the 
engine, chiefly relating to dimensions of wearing surfaces and the 
strength of parts, that engineers rarely fix. It is the custom of 
some, though, to ask each builder what he intends to furnish in 
respect to certain details, usually about as follows: Diameter 
and length of bearings, diameter and length of crosshead pins, 
diameter and length of crank pins, diameter of shaft in the body, 
dimensions of crosshead shoes, length of connecting rod, diam- 



72 STEAM POWER PLANTS 

eter and face of flywheel (both may be fixed by the engineer), 
weight of flywheel, weight of engine bed, weight of entire engine. 

When these data are received from each builder the engineer 
can tabulate them and compare the proportions of the engines 
offered. If any part of an engine differs from that of others 
enough to warrant such a course, the engineer can ask the reason 
for this deviation, and if it is not a good one the builder can be 
requested to modify his design, or the bid can be rejected. The 
engine builder should be asked to furnish a blue-print or draw- 
ing of some kind showing a plan and elevation and the principal 
dimensions of the engine he proposes to furnish. 

Regarding details of construction of engines, most American 
engines are built after standard designs adopted by each builder, 
and not much attention is usually paid in specifications to these 
details when builders of established reputation are bidding. 
Most builders furnish catalogues containing illustrations of the 
details of various parts of their engines, such as the valves, valve 
gear, governor, piston, main bearings, crosshead, etc. If an engi- 
neer is obtaming bids on an engine the details of which are un- 
known to him, such illustrations can be asked for. When about 
to execute a contract with a builder, it can be stated in the con- 
tract that the details of construction are to correspond in design 
with drawings or blue-prints or catalogue sketches furnished by 
the builder. 

There are a great many minor details of an engine, such as oil 
cups, sight-feed lubricators, throttle valve, relief valves on the 
cylinders to prevent them from being damaged by water, cylinder 
lagging, steam and vacuum gauges, gauge board, provision for 
attaching the indicators to the cylinders, etc., that have to be 
looked after, and many builders furnish a printed specification 
which refers in more or less detail to some of these matters. This 
specification can be asked for and made part of the contract, but 
before so doing care should be taken that it does not conflict with 
the specification issued by the engineer. 

The character of materials used in engine construction is not 
usually given much attention in an engineer's specification, but 
recently the materials of which shafts of large engines are made 
is receiving more thought, and the kind of metal used, and its 
treatment, is frequently specified. The most advanced practice 
is found, probably, in the fluid-compressed hollow-forged treat- 




Section through Boiler Room 



Longitudinal Section. 
Plate 8. — Power Plant, Massachusetts General Hospital, Boston, Mass. 

DEAN & MAIN, ENGINEERS. 



STEAM POWER PLANTS 73 

merit, perfected by the Bethlehem Steel Company. The molten 
steel is poured into a cylindrical mold and subjected to an enor- 
mous pressure while cooling, so as to diminish the blowholes that 
frequently occur in the ordinary method of casting. The ingot 
is cooled slowly and the impurities usually collect at its axis; after 
it has cooled, an axial hole is bored through it to remove these 
impurities. The ingot is then reheated and a mandrel is slipped 
through this hole, after which it is forged under a slow-moving 
hydraulic press, the action of which penetrates much more deeply 
into the metal than is the case with the blow of a steam hammer. 
After forging, the ingot is annealed to remove internal strains 
and improve the structure of the metal, which is then machined 
to size. Sometimes the shaft is oil-tempered after annealing. 
Open-hearth and nickel" steels are used, the small percentage of 
nickel added tending to raise the physical properties of the mix- 
ture. A large number of recent important engines for mill and 
electric power-house service have been equipped with shafts made 
in this way. 

♦The time of delivery of an engine should be given in a specifi- 
cation, and with large engines the builder is sometimes required 
to furnish a man to operate the engine for a short period after it 
is erected. If the engine room is to be fitted with a traveling 
crane operated by electricity or by hand, it is well to notify the 
engine bidders to that effect, as the use of a crane reduces the 
cost of erecting engines, and the owner should have the benefit 
of this. 

In regard to steam piping, the engine builder usually supplies 
and connects the piping between the cylinders in a compound 
or triple-expansion engine. In large compound engines, particu- 
larly of the cross-compound type, that is, with the cylinders placed 
side by side and driving separate cranks, it is frequently the 
custom to place a valve in the pipe carrying the exhaust steam 
from the high-pressure to the low-pressure cylinder, and to run a 
branch from the high-pressure steam pipe to this exhaust pipe, 
connecting with it at a point between the low-pressure cylinder 
and the valve mentioned. With this arrangement the high-pres- 
sure cylinder can be cut out, and the engine driven by the low- 
pressure side alone. The pipe conveying high-pressure steam 
to the low-pressure cylinder is usually provided with a pressure- 
reducing valve as well as an ordinary stop valve. By connecting 



74 STEAM POWER PLANTS 

the exhaust from the high-pressure cylinder, at a point between 
that cylinder and the stop valve between the two cylinders, with 
the main exhaust pipe, and by placing a valve in the exhaust from 
the low-pressure cylinder, the low-pressure cylinder can be en- 
tirely cut out and the engine driven by the high-pressure cylinder. 
The advantage of such an arrangement in the event of the break- 
down of one side of the engine is obvious. An arrangement of 
this kind is shown very nicely in Fig. 18. This practice is more 
common in mill and factory work than it is in electric generating 
plants. 

For electric work, where revolving parts of dynamos are 
mounted on the engine shaft, as is the custom in directly con- 
nected work, the specifications should require the engine builder 
to cut a key-way in the shaft. The dynamo builder usually sup- 
plies a key for keying the armature of the dynamos on the engine 
shaft. The dynamo and engine are sometimes shipped by their 
respective builders to the site of the power plant and the engine 
or the dynamo builder fits the armature to the shaft. In other 
instances the shaft is shipped to the dynamo builder and is jut 
on the shaft by the latter. The specification should state what 
each builder is to do in this respect. 

A specification often asks what steam consumption the builder 
of an engine will guarantee. If a guarantee as to steam consump- 
tion is to be made, it should be of the following general form: 

" The engine is guaranteed to consume not more than ■ 

pounds of steam per indicated horse-power per hour when de- 
veloping - — — horse-power when running at a speed of 

revolutions per minute with a steam pressure of pounds 

above the atmosphere, and with a back pressure of pounds 

above the atmosphere." The specification should state that in 
case of dispute the steam pressure is to be the average pressure 
as obtained by a throttled steam gauge connected to the steam 
pipe close to the throttle valve, or by means of a steam-pipe dia- 
gram obtained by attaching an indicator to the location named. 
If the engine is to run condensing instead of with a back pressure 
above the atmosphere, the vacuum to be carried should be stated. 
The usual vacuum is from 26 to 27 inches of mercury, depending 
upon the size of the engine. If the engine is provided with 
steam jackets and reheating receivers, it should be stated that 
the steam used by them is to be included in the consumption of 



STEAM POWER PLANTS 75 

the engine. If the engine is to run condensing, the steam used 
by the air-pump should be included, provided the engine builder 
supplies and is thereby responsible for the efficiency of the con- 
denser. Sometimes, when condensers are not supplied by the 
engine builder, the steam used by the air-pump is not con- 
sidered as being part of the steam used by the engine. If the 
air-pump steam is or is not to be considered as part of the engine 
consumption, a statement to that effect should appear in the 
guarantee. It is usually the custom to measure the degree of 
vacuum obtained by a gauge attached to the exhaust pipe of 
the engine close to the engine, and a specification should state 
that the vacuum is to be so measured. 

A fair guarantee to ask concerning the regulation is that the 
speed of the engine shall not vary more than 1J per cent above 
or below the normal speed under any condition of load. The 
builder should guarantee the workmanship and materials to be 
of the best, and agree to make good at his expense any defects 
in the engine, not due to neglect, that develop during the first six 
months or year it is in operation. 

The accompanying specification was prepared by Mr. Nicholas 
S. Hill, Jr., M. E., and it is printed here with his permission. It 
should be understood that it was drawn for the purpose of ob- 
taining a small automatic high-speed engine for a private cor- 
poration that obtained bids from several reliable builders whose 
engines were well known. 

SPECIFICATION FOR A 300-I.H.P. NONCONDENSING ENGINE. 

In the following specification the noun "Company" is used to designate 
the purchaser, the (purchaser's name and address). The noun " Builder" is 
used to designate the seller, the contractor, the manufacturers of the engine. 

Rejection. — The Company reserves the right to reject any or all bids. 

Engineer. — The interpretation of the specifications hereinafter set forth 
shall be left to the Engineer appointed by the Company, and the inspection 
of all materials furnished and all tests for the determination of the fulfillment 
of the guarantee herein contained shall be made under the direction of the 
said Engineer. 

Test. — The engine will be tested at such time, after the erection and com- 
pletion of engine and generator, as the builders may select and after the Engi- 
neer shall have received at least one week's notice. The Company will furnish 
the necessary fuel, oil, and supplies, and the contractor will be required to 
furnish the indicator rig and prepare the engine for test. The Engineer will 
furnish the indicators. A run of ten hours will be made and the load will be 



76 STEAM POWER PLANTS 

maintained as nearly as possible at 300 I.H.P. The conditions of the test 
will be fixed at the time of the signing of the contract as agreed between the 
Engineer and the Builder. 

Kind of Service. — The engine is intended to operate a generator driving 
motor-driven tools located in the shops of the Company. 

Location. — The engine is to be located on foundations in the power house 
of the (name) Company at (place). 

Type of Engine. — The engine desired is of the single- valve, tandem com- 
pound, flywheel governor, automatic cut-off type, with extension sub-base, 
direct connected to a (name) generator, size No. — , 200-kw. 250-volt generator. 

Conditions of Erection. — The Builders will furnish and erect engine on 
foundation supplied by the Company. The engine may be unloaded directly 
from car at the door of the power station within 15 feet of the foundation. 
The station is equipped with a traveling crane of five tons capacity. The 
armature for the generator will be placed on shaft at the power house. 

Conditions of Operation. — The engine is to run noncondensing at 200 
r.p.m. Steam pressure 125 pounds above the atmosphere. Back pressure 
15 pounds absolute. The maximum load for which engine is intended equals 
400 I.H.P. The engine is to operate at highest efficiency with load equal 
300 I.H.P. The average load will equal 175-200 I.H.P. 

Size of Cylinders. — The cylinders shall be approximately 18 inches and 
29| inches by 18 inches, or 18| inches and 30 inches by 17 inches. 

The volumes of cylinders furnished shall be not less than the volumes 
herein specified, and the ratio of the cylinder volumes shall be between 2.6 
and 2.8. 

Speed Regulation. — The speed regulation shall be within 1.5 per cent above 
or below normal. 

Piston Speed. — The piston speed shall be not less than 560 feet per minute 
nor more than 600 feet. 

Clearance. — The clearance shall not exceed 8 per cent. 

Indicator Attachment. — Brass piping for indicator with three-way valve 
is to be furnished for both high- and low-pressure cylinders. 

Dimensions and Weights. — The Builder shall furnish the following data 
in regard to engine: 

Total weight of engine. 

Total weight of heaviest part. 

Total weight of flywheel. 

Diameter and length of main bearings. 

Diameter and length of crosshead pins. 

Diameter and length of crank pins. 

Diameter of main shaft in body. 

Diameter and face of flywheel. 

Length of connecting rod. 

Blue-prints, Template, Specifications. — The Builder shall furnish blue- 
print of engine and foundations which shall form a part of these specifications 
after acceptance of proposal. A foundation template and foundation bolts 
shall be furnished by the Builder. The foundation bolts to be provided with 
washers at least 10 inches square and to be threaded for two nuts at top. The 



STEAM POWER PLANTS 77 

Builder shall also furnish specification of the lubricators, oil cups, tools, etc., 
to be supplied with engine. 

Materials. — All materials used in the construction of the engine to be the 
best of their various kinds and to be in strict conformity with the latest modern 
practice. 

Guarantee. — The engine shall be guaranteed to consume not more than 
24 pounds of steam per I. HP. per hour, when developing 300 H.P., when 
running at a speed of 200 r.p.m. with a steam pressure of 125 pounds above the 
atmosphere and with a back pressure of 15 pounds absolute. 

The Builder shall also guarantee to make good any or all defects developed, 
within 150 days from the time of starting engine, which may be due to inherent 
defects in materials or faulty workmanship and design, provided such defects 
are developed when engine is running at less than 50 per cent overload. 

Painting. — All unfinished iron work about engine shall be filled, rubbed 
smooth, and receive one coat of paint before leaving shop. A second coat is 
to be applied after erection and finally a finish coat highly enameled. The 
color is to conform with machinery already in place in the engine room. 
Quality of paint to be such as to insure against blistering, peeling off, or fading, 
and shall be satisfactory to the Engineer. 

Covers. — The engine is to be supplied with a neatly fitting and well-made 
oiled-canvas cover to be approved by the Engineer. 

Time of Delivery. — The Builder shall specify the earliest possible date of 
delivery. 

Price. — The price submitted by the Builder shall include delivery and 
erection in conformity with the preceding specification. 

The following specification was prepared by an engineer for 
the purchase of Corliss engines at a public letting, where anyone 
could submit a tender that wanted to; hence the specifications 
go into details a good deal more than is necessary, perhaps, for 
private work, where the bidding can be confined to experienced 
and trustworthy builders. 

SPECIFICATIONS FOR CORLISS ENGINES. 

Intent of Specifications. — The intention of these specifications is to pro- 
vide for furnishing and installing, complete and ready for operation in a man- 
ner satisfactory to the engineer, three simple Corliss type engines, each to be 
as hereinafter specified, for direct connection to direct-current generators, and 
certain other apparatus, all as hereinafter specified, in the power plant for 
at . The owner will provide a 20-ton hand-operated traveling crane. 

Time of Delivery. — The engines and other apparatus called for under this 
contract shall be delivered and erection begun on the date when the engine 
room is ready to receive them, as determined by the engineer; and the con- 
tractor shall deliver all of the apparatus called for in this specification and 
have it ready for operation within two months after said date. The engine 
room will not be ready to receive the engines before . 



78 STEAM POWER PLANTS 

• 

Dimensions. — Each bidder must furnish with his proposal the following 
data and dimensions in full of each engine that he proposes to supply: 

Dimensions of cylinder. 

Minimum thickness cylinder walls. 

Clearance of cylinder. 

Width of piston face. 

Diameter of steam and exhaust pipes. 

Diameter of piston rod. 

Length of connecting rod. 

Diameter and length of main and outboard bearings. 

Diameter and length of crosshead pin. 

Area of crosshead shoes. 

Diameter and length of crank pins. 

Diameter and weight of flywheel. 

Diameter of shaft in middle. 

Weight of entire engine. 

Guaranteed engine friction in per cent of rated load. 

Guaranteed steam consumption at full normal generator load. 

Guaranteed speed regulation in per cent of no-load speed. 

Guaranteed momentary variation in speed under any change in load from 
no load to full load. 

Relation of Engine and Generator Builders. — Within two weeks after the 
generator contract is let the generator builder shall send to the engineer in 
duplicate, and to the engine builder, shop drawings of the generator with the 
weights of the armatures. The engine builder will design the shafts, bearings, 
and foundations to accommodate the generators. The generator builder shall 
at the proper time furnish the engine builder with a gauge giving the exact 
diameter of the armature bore and a drawing showing location and size of 
the key-way. The engine contractor will then be responsible for furnishing a 
shaft and key of the size given by the gauge and drawings. The shaft must 
fit the armature in a manner satisfactory to the engineer. The generator 
contractor shall force the armature upon the engine shaft after delivery at 
the building. The engine contractor and generator contractor shall cooperate 
as directed by the engineer in erecting each engine and generator. The en- 
gine contractor and generator contractor shall each be individually respon- 
sible at all times for all parts of the apparatus which each is to furnish. The 
engine builder will furnish foundation bolts, inclosing pipes, and anchor plates 
for both engines and generators, and he shall construct the engine and generator 
foundations. 

Inspection. — The engineer reserves the right to inspect the engines at 
any time during their construction and installation, and the contractor shall 
afford representatives of the engineer all facilities to this end. 

Drawings. — Bidders shall submit with their proposals blue-prints in dupli- 
cate showing both in plan and elevation dimensioned drawings of the general 
arrangement and the principal dimensions of engines they propose to supply. 

Within thirty days after the engine and generator contracts are let the 
engine builder shall furnish to the engineer four sets of blue-prints for the 
foundations for the engines and generators, together with detail drawings of 



STEAM POWER PLANTS 79 

all foundations, bolts, anchor plates, nuts, washers, etc.; these will be required 
at the earliest possible moment for use in preparing the working drawings. 
Should the engineer ask for them the contractor shall, within thirty days after 
the contract is let, submit a complete set of shop drawings showing the engine 
frames, cylinders, valves, valve gear, piston, crosshead, flywheel, and bearing, 
and of such other parts as may be called for, which drawings shall be approved 
by the engineer and returned to the bidder before work is commenced. If the 
designs submitted are unsatisfactory to the engineer, they shall be changed to 
conform with the requirements of these specifications, and the engines shall 
be constructed in accordance with these requirements. It shall be distinctly 
understood that the approval of each or any drawings will not relieve the 
contractor from the requirements of the specification. 

Type. — Engines shall be simple Corliss type engines as hereinafter speci- 
fied, and adapted for the duty demanded in driving direct-current electric 
generators, the armatures of the engines being mounted on the engine shafts. 

Capacity. — The normal rating of two of the generators will be 500 kw. 
at 100 r.p.m. 

The normal rating of one of the generators will be 250 kw. at 100 r.p.m. 

Each engine must be capable of driving continuously its respective genera- 
tor at normal output and at normal speed with an initial steam pressure of 
125 pounds above the pressure of the atmosphere at the throttle valve and 
a back pressure in the exhaust pipe outside of the cylinder of 2 pounds above 
the pressure of the atmosphere. The engines shall be sufficiently strong in 
all their parts to do this work, and the valve gear must be so designed to per- 
mit the generator overloads mentioned (50 per cent) to be maintained. 

Speed. — The normal speed of the engines shall correspond to the normal 
load speeds of the generators given above. 

Steam Pressure. — The steam pressure at the throttle valves of the engines 
will be 125 pounds. The engines must be sufficiently strong to stand a work- 
ing pressure of 150 pounds should it be desirable to raise the steam pressure to 
that extent. 

Design. — The engines must in every way conform to the best modern 
practice. 

Beds. — The bed of the engine must be of heavy design, with a single cast- 
ing containing and cast with the main pillow block and inclosing the crank 
pits. The girder type of frame will not be accepted. The bed shall have a 
solid bottom and be well stiffened with ribs. The crank pit shall be designed 
so as to catch and retain the oil, and all exposed flat surfaces adjacent to 
the crank pit shall have a gradual slope towards the crank pit for draining 
into the same. Guides shall be designed to drain into crank pit only. Means 
shall be provided for draining off the oil through piping as directed. The 
entire bed must be of massive design, with smooth surfaces and well-rounded 
corners, and must extend to the foundation at all points. The bed plate shall 
be anchored by a sufficient number of properly spaced foundation bolts seat- 
ing on raised and counterfaced bosses. 

Guides. — Guides shall be constructed to insure perfect rigidity and align- 
ment and give access to working parts. They may be cast with bed plate, or 
separately and bolted to the latter. The guides must be accurately bored, 



80 STEAM POWER PLANTS 

true to the axis of the cylinder. If guides are cast separate from the bed plates, 
they shall be bored and both ends faced off at one setting. If cast in one 
piece, guides shall be bored and cylinder ends faced off at one setting. Oil 
receptacles shall be provided at front end of the lower guide arranged to drain 
into the crank pit. 

Shafts. — The engine shaft shall be of high-quality open-hearth steel 
hydraulically forged. The crank shaft shall be ample in size to carry the 
weight' of the flywheel and armature, and of ample length to afford proper 
working space. Shafts shall be free from all defects, turned at the proper 
diameter, and polished when exposed. The engine shafts shall be suitable for 
the particular make of generator purchased. That part of each shaft sup- 
porting the flywheel and armature shall be of greater diameter than the 
bearings so that the radial distance from the center of the shaft to the bottom 
of the key-way shall be greater than the radius of the shaft at the bearing by 
one-half inch. Change in diameter shall be an easy taper of 15 degrees with 
axis of shaft, if space will permit. The ratio of the diameter of the journal 
to its length shall be not less than 1 to 1.6 and not more than 1 to 2. 

Cranks and Crank Pins. — Cranks shall be of the counterbalanced disk type 
turned and polished on the face and rim. Crank disks shall be forced upon 
the shafts by hydraulic pressure and properly keyed. Crank pins shall be of 
open-hearth forged steel, shouldered and forced into crank disks by hydraulic 
pressure. Crank pins shall be of such a size that the effective pressure on the 
projected area of the pin shall not exceed 800 pounds per square inch. 

Cylinder Sizes. — Bidders shall state in their proposals what cylinder sizes 
they propose to use. The use of a relatively large cylinder diameter and short 
stroke will not be permitted. Cylinders shall be of such a length between 
heads as not to require an unusually long piston. 

Valves. — Engine valves shall be of the multiported Corliss type, so de- 
signed that they will not make a shoulder in the seats. Valves shall be 
machined and ground on a grinding machine to the proper diameter to insure 
tightness without undue friction. Valves must be so designed that they may 
be removed easily through the openings in the back of the cylinders without 
disturbing the valve gear. Valve setting marks shall be made on the back of 
valves. Valve stems shall be of steel accurately ground to gauge and operat- 
ing in bronze bushings. Valve stems shall be provided with suitable packing, 
and in addition it is desired that flat steel disks carefully machined and ground 
be shrunk on the valve stems so that when they bear upon the valve bonnet 
the joint will be steam-tight. 

Cylinders. — Cylinders shall have heavily ribbed walls of ample strength. 
The cylinder walls shall be sufficiently thick that when they are bored to 
one-half inch larger diameter the tensile strain in the metal will not exceed 
2000 pounds per square inch with a steam pressure of 125 pounds in the 
engine cylinder. They shall be of close-grained air-furnace iron as hard as 
can be machined, free from defects of any kind. Cylinders to be so designed 
as to permit expansion to occur at rear end through suitable guides. The 
piston bore shall be straight, of uniform diameter from end to end, and its 
surface is to be smooth, even, and free from flaws and defects. Ends shall 
be slightly counterbored. Cylinder heads and pistons shall be faced to insure 



STEAM POWER PLANTS 81 

a definite clearance at each end. Clearance shall be reduced to a minimum. 
Flat surfaces must be strongly ribbed. Cylinders shall be drilled and tapped 
for indicator cocks. Cylinder heads shall be machined all over their inside 
surfaces, and they shall be provided with a polished false cover. Cylinders 
shall be covered with 85-per-cent carbonate-of-magnesia nonconducting ma- 
terial and then lagged with heavy planish ed-steel lagging to extend down to 
floor. Corner strips of polished steel, fastened with machine screws, shall be 
provided. 

Valve Gear. — The valve gear shall be of the Corliss type with dashpots. 
Dashpots shall be of the noiseless, self-contained type of approved design. 
The entire valve gear shall be noiseless in action. Steam and exhaust valves 
shall be operated by means of separate eccentrics, with gear so designed that 
the cut-off can occur as late as three-quarter stroke. Valve gear shall have 
an approved releasing clutch or hook rod for both steam and exhaust so they 
may be operated by hand. All parts of valve gear must be adjustable to 
take up wear without changing the length of the connections. All pins in the 
valve gear shall be forged steel hardened and ground to gauge. All link and 
rod ends in valve gear shall be of phosphor bronze with graduated wedge 
adjustments. The wedges shall have a full bearing surface on the boxes. 
End set-screw adjustments will not be accepted. All stub ends shall be 
screwed upon the rods and locked by means of case-hardened hexagonal sleeve 
nuts. Hook rods shall be of forged steel. All similar parts of the gear shall 
be interchangeable. The drip pipes for the valves shall be brass nickel-plated. 
They shall be carried below the floor as directed. 

Governor. — Governors in design and operation shall be equal to the best 
practice. They shall be so constructed that the speed of the engines will not 
vary more than three revolutions per minute under any change in load from 
no load to full load applied suddenly or gradually, and shall not be so sensitive 
as to cause racing or hunting. Their action shall be controlled if necessary 
by a suitable oil dashpot. The bottom of the governor spindles, if of the 
vertical flyball type, shall rest in a case-hardened steel step bearing. Upper 
end shall be provided with an oil hole fitted with a one-pint sight-feed lubri- 
cator. Governor weights, if of the inertia type, shall oscillate upon roller 
or ball bearings. Governor pins shall be of hardened steel ground true to 
size. 

Eccentrics. — Steam and exhaust valves on all cylinders shall be operated 
by separate eccentrics. Eccentric straps shall be split and lined with Babbitt 
metal hammered in and turned to a smooth finish. Straps shall be held to- 
gether by two through bolts with lock nuts. Each eccentric shall be held by 
at least two set screws. Eccentric straps shall be fitted with deep oil trough. 
Eccentric rods shall be of forged steel polished and fitted with adjustable box 
end of bronze. Each rocker and shaft shall be fitted with one-pint sight-feed 
oil cup. 

Flywheel. — Flywheels shall be of cast iron, heavy, sound, and perfectly 
balanced. The wheels shall be cast in two sections with joints planed to a 
proper fit. The periphery and both sides of the rim shall run true. Face 
of rims shall be provided with barring holes, and barring device of approved 
design shall be provided for each engine. Rim joints shall be made with 



82 STEAM POWER PLANTS 

heavy steel links or arrowhead keepers set into' the sides of the rim at each 
joint. Through bolts shall be used in the hub. Bolts and links shall be of 
open-hearth steel. Bolt holes shall be drilled out of solid metal or they shall 
be reamed out to size. The flywheels shall be of ample size and weight to 
give proper regulation and to properly control the parallel operation of the 
generators. The wheels shall be so constructed that under no condition will 
intense stress due to improper manufacture occur. 

Connecting Rod. — Connecting rod shall be open-hearth steel of ample 
strength, accurately turned and polished. Crank and crosshead ends of rod 
shall be of solid type. Boxes at each end of connecting rods shall be provided 
with wedge adjustments controlled by screws for taking up wear in such a 
manner as to preserve constant the length between the crosshead and crank 
pins. Crank pins shall be lined with Babbitt metal hammered in and bored 
out, crosshead boxes to be of phosphor bronze. 

Crosshead and Pins. — Crosshead shall be of cast steel, and it must be 
connected to the piston rod in an approved manner. The crosshead shoe must 
have a large wearing surface, must be lined with Babbitt metal, and must 
be provided with wedge adjustments for taking up wear by means of through 
bolts set up by lock nuts. Shoe area to be such that pressure will not be over 
35 pounds per square inch. End screw adjustments and fastenings will not 
be accepted. The crosshead pin shall be of open-hearth steel with ground 
taper fits on front and rear side of crosshead held iu position by steel jamb 
nut. 

Piston Rod. — Piston rod of each engine must be of open-hearth forged 
steel ground to- gauge. Rod must be connected to the piston and to cross- 
head to permit adjustment for equal clearances. Means shall be provided 
for preventing piston rod from turning in the crosshead. 

Packing. — Stuffing box for each piston rod must be provided with an 
approved metallic packing so designed as to be capable of removal without 
removing the piston. 

Piston. — Piston must be of approved design with cast-iron self-adjusting 
packing rings. Piston rods shall be forced into the pistons and be provided 
with a steel check collar or other equivalent means, doubly secured to abso- 
lutely prevent it from working loose. Junk ring to be so arranged that pack- 
ing may be examined, removed, or replaced without removing the piston from 
the cylinder. 

Bearings. — The main and outboard bearings shall be of pillow-block type 
adjustable in a horizontal direction. Bearings must be provided with Babbitt 
cast into dowel pockets, well hammered in, turned, and scraped. Both bear- 
ings shall be capable of being removed by raising shaft | inch. Wear shall be 
taken up by means of wedges on both sides having full bearing surface upon 
the shells. Set-screw adjustment will not be accepted. The pedestals for 
the outboard bearings shall extend downward sufficiently below the floor fine 
so that the finished floor can be built in around the pedestal and cover the 
foundation. A polished false cover shall be fitted over the outboard ends of 
shafts. Bearings shall have heavy caps provided with large handhole and 
holding-down bolts. Caps shall be tapped for eyebolts which shall be sup- 
plied for each engine. The end of outboard bearings adjacent to the genera- 



STEAM POWER PLANTS 83 

tors shall have means for preventing the oil from working its way into the 
shafts. The bearings shall be lubricated by rings or chain extending into an 
oil reservoir in the pillow block. The resultant bearing pressure shall not 
under any condition of pressure exceed 180 pounds per square inch of pro- 
jected area. Pressures shall be considered as the vertical component of the 
125 pounds pressure on the crank pin plus the pressure due to the weight of 
the flywheel, shaft, eccentrics, crank disks, and armature. Contractor shall 
provide some approved method of oiling the main bearings of each engine. 

Cylinder Fittings. — Each cylinder shall be provided with polished nickel- 
plated brass drip valves and piping run below the engine-room floor. Each 
cylinder of each engine shall be provided with indicator piping with three- 
way cock, all of brass nickel-plated. 

Oil and Water Drips. — Proper means shall be provided to collect all 
dripping oil and water. All pockets in each engine where oil and water will 
collect and all points requiring the drainage of oil or water shall be provided 
with a drip system, the design of which shall be furnished and approved. 
Pipe and fittings above the floor shall be of polished brass (iron-pipe size) 
nickel-plated. The oil drips for each engine shall unite in a common oil 
main one inch in size which shall be run to a point under the floor. There 
shall be a separate drip system for dirty drips, to be run to point under floor 
where the steam fitter will connect. Each opening in the floor for all pipes 
shall be protected by a nickel-plated cast-brass collar. Contractor shall do 
all cutting for all pipes. All necessary nickel-plated brass oil or water drip 
piping shall be supplied. 

Cylinder Base Pans. — Cast-iron base pans shall be provided under each 
cylinder and valve gear so as to collect all oil and water. 

Oil Pans. — The contractor shall supply proper and approved pans of 
heavy polished brass as may be required for the valve gear, rocker gear, shaft, 
gear, guide barrels, and for other points as may be necessary. 

Splashers. — The contractor shall provide for each engine oil guards or 
splashers which shall be made of heavy planished sheet steel with polished 
steel corner pieces. The splashers shall be so constructed that they will com- 
pletely cover the opening opposite the crosshead and house the crank and 
connecting rod. Approved doors giving proper access to all parts shall be 
provided in such oil guards. The splashers shall be made with flanged sec- 
tions properly stiffened with angle iron, and shall be so constructed as to 
be easily removable. The joints shall be so constructed that no oil will 
work through them. Whenever openings are allowed the edges shall be well 
strengthened and protected by planished steel strips. A similar arrangement 
shall entirely close the eccentric, and this must be provided with sliding covers. 
The bottom of eccentric hoods shall be furnished with a drain for the drip 
pipe, and the entire structure must be securely fastened to the bed. 

To protect the generator from oil creeping along the shaft, thin disks shall 
be furnished rotating just inside the eccentric hood, so that oil may be thrown 
into the hood before it can go farther. The space between the disk and shaft 
shall be so packed that no oil can creep through underneath. 

Indicators. — The'contractor shall furnish two outside spring indicators 

of the latest pattern, the pair in neatly finished box with lock and key. Each 



84 STEAM POWER PLANTS 

indicator shall be provided with two indicator cords and the followings springs: 
40 pounds, 60 pounds, and 80 pounds, one extra drum spring, and a set of 
graduated scales, one for each spring, and 500 metallic-faced cards. The con- 
tractor shall also supply three approved reducing motions, one for the small 
engine and two for the large engines, attached to engine, which can be thrown 
in or out while engine is running. Each engine shall be so fitted that the 
indicator and reducing motion may be connected to them. 

Wrenches. — The contractor shall supply a complete set of neatly finished 
case-hardened wrenches for all engines, also such eyebolts as may be needed. 
Wrenches and eyebolts shall be mounted on a neatly finished and varnished 
wrench board of black walnut with beveled edges. Boards shall be mounted 
on the wall of engine room where directed by the engineer. Wrenches shall 
not be used in erecting the engine. 

Oiling Devices. — Each cylinder shall be provided with approved and posi- 
tive means for oiling. Each engine shall be provided with adequate and proper 
means for lubricating all moving parts. The contractor shall place ample 
sight-feed oil cups wherever they may be required and as directed by the 
engineer. The crosshead pin shall be provided with neatly finished and 
approved wiping device. An approved oiling device shall be furnished for 
each crank pin with necessary standard. Wherever grease cups are required 
compression cups shall be provided. Oil cups shall be of glass body, arranged 

for gravity and for hand feed, and shall be of make. Grease cups shall be 

of heavy-pattern compression type. All parts requiring lubrication shall 

be provided with receptacles for catching oil when the oil may be supplied 
by the oil filtering and circulating system, described under " Central Oiling 
System." All oil cups, pipes, and fittings above the floor shall be brass nickel- 
plated. 

Central Oiling System. — The contractor shall furnish and install, complete 
and ready for operation, an Automatic Gravity Oiling System, for supplying 
machinery oil to each point of lubrication on two 500 kw. and one 250 kw. 
Corliss engine generating units and two oil sinks. Also a gravity cylinder-oil 
system, for supplying cylinder oil to two oil sinks. 

A plan showing the location of the generating units and oil sinks, also the 
approximate iocation of pumps, filter, tanks, etc., may be seen at the office 
of the consulting engineer. This arrangement is subject to such modification 
as may be found desirable, to conform to building conditions. Trenches will 
be furnished by the builder, and combination oiling system sight feeds on the 
engines will be furnished by the engine builder. Steam connection to pumps 
will also be provided under a separate contract. The central oiling system 
will include the following apparatus : — 

One gravity oil filter. 

Two oil storage reservoirs. 

Two steam-driven oil pumps. 

Two brass oil sinks. 

Two drip pans or pumps and filter. 

One combination receiver and pump governor. 

All piping, valves, unions, fixtures, appliances, labor, and material necessary 
to make a complete installation. 



STEAM POWER PLANTS 85 

Oil Filter. — Furnish and install one No. 18 multiple-type oil filter, 

having a daily filtering capacity of not less than 250 gallons. Body of filter 
to be constructed of heavy galvanized sheet steel and jacketed with Russian 
iron and polished steel angles. Filter to be equipped with automatic water 
overflow. 

Oil Storage Reservoirs. — Furnish and install two 75-gallon oil storage reser- 
voirs, to be supported in a horizontal position by not less than two brackets. 
They shall be constructed of not less than No. 10 B.W.G. galvanized iron 
and equipped complete with all necessary flanged pipe openings, oil gauges, 
automatic overflow, etc. 

Oil Pumps. — Furnish and install two steam-driven duplex oil pumps, full 
brass fitted and equipped with valves suitable for handling oil. Each pump 
to be mounted on suitable angle-iron base. 

Oil Sinks. — Furnish and install two oil sinks, of heavy polished brass 

with beaded edges and supported on polished brass brackets. Each sink 
shall be provided with two bibcocks, removable tray with strainer and drain 
connection. 

Drip Pans. — Furnish and install polished-brass drip pans for pumps and 
filter turned up f inch and wired. Each pan to have necessary drain con- 
nections for carrying away drips. 

Oil-feed Lines. — Furnish and install a machinery-oil supply line extending 
from the oil storage reservoir through the trenches to each engine and to two oil 
sinks. All branch feed lines to be provided with a gate oil valve, located just 
above the engine-room floor. Another supply line shall be installed from the 
cylinder oil storage reservoir to the two oil sinks. All piping above the floor 
line, extending up to and on the engines and oil sinks, shall be drawn-steel tub- 
ing, fully nickel-plated and connected up with nickel-plated pipe fittings. All 
pipes, fittings, valves, etc., on the engines shall be supported with nickel-plated 
concealed screw hangers, holding the pipe away from the engine frames a dis- 
tance of about 1 inch. 

Drain Pipe. — Furnish and install a used-oil return drain fine, extending 
from the main return on the four generating units and two oil sinks to the 
receiver and pump governor, also a line for returning any excess oil delivered 
to the reservoir. 

Pump Connections. — Suction and discharge headers on pumps to be ar- 
ranged with necessary connections, valves, etc., so that either pump may be 
used for delivering dirty oil from the receiver to the filter, or filtered and 
cylinder oil from the filter to the overhead storage reservoirs. A connection 
for delivering new oil from the barrels into the system shall be made to the 
suction header and extended as determined at the time of installation. All 
pipe around pumps to be brass nickel-plated and all connections to pumps, 
filters, tanks, etc., to be made with ground-joint brass unions. The ends of 
all pipe are to be properly reamed, joints being made perfectly oil-tight, and 
plugged tees and crosses shall be used in lieu of elbows and tees. 

Pump Foundation. — Foundations for pumps and filter to be of selected red 
brick set in Portland cement mortar-faced with best-quality white American 
enamel brick with rounded corners, set in white mortar. Provide 4-inch 
rubbed bluestone cap for foundation. 



86 STEAM POWER PLANTS 

Oil Pumps. — Furnish and connect on each of the three generating units 

one three-feed oil pump connecting with both ends of the cylinder and 

with the metallic piston-rod packing. 

Finish. — The engine shall be finished in three styles, — polished surfaces, 
machined surfaces, and plain surfaces. 

Polished surfaces shall show no tool marks and be highly polished. These 
surfaces shall include such surfaces as have been elsewhere specified as polished 
surfaces, also the entire valve gear, the cylinder covers, connecting rod, gov- 
ernor rods, valve bonnets, dashpot covers, and throttle-valve bonnet. All 
exposed machined surfaces shall be free from tool marks. Plain surfaces shall 
be filled and rubbed down as many times as necessary to secure a smooth and 
even finish and put them in proper condition for painting. 

Throttle Valves. — The throttle valves of all engines shall be of extra-heavy- 
weight iron-body globe valves with removable bronze seats and bronze mount- 
ings, with bodies tapped for drip pipes. Valve seats shall be ground so as 
to be steam-tight. Valves shall be of the outside screw type. 

Painting. — The engine builder shall paint and varnish all engines and 
generators. All parts of the engines not polished or covered with planished 
material must be thoroughly cleaned, primed, rubbed down, and given two 
coats of lead and linseed oil at the shop. After the engines are erected and 
ready for operation the engines and all iron castings in each generator shall 
be filled and rubbed down as many times as is necessary to give a smooth and 
even finish. The work shall be then given one coat of selected coach color, 
striped with gold leaf, which is to be followed by two coats of coach body 
varnish. 

Railing. — The contractor shall supply and install for each engine a railing 
of 1\ inch pipe which shall be run around both sides of the flywheel and genera- 
tor pit and terminate in an approved manner. All pipe stanchions and fit- 
tings and railing shall be of polished steel. The posts to be screwed into floor 
polished flanges. 

Foundations. — The space available for engine foundations is shown on 
the accompanying plan, and it is proposed to use a continuous concrete block 
for the foundations, which the engine builder shall construct. If in the opinion 
of any bidder additional mass is necessary to prevent vibration, the founda- 
tions may be extended in a horizontal direction and the bidder shall figure 
upon such extension and notify the engineer in his proposal of what increase 
he deems necessary. If no such notice is given, it shall be assumed that the 
space provided by the engineer for foundations is satisfactory. The founda- 
tions shall be separated from the concrete below and from column footings 
and from all other building material by a bed of dry sand about 4 inches thick 
extending beneath and around all sides of the foundation. 

Concrete to consist of one part Portland cement, three parts sand, and four 
parts broken stone that will pass a two-inch ring. Material to be mixed as 
directed and sufficient water added to make the mixture run lightly. Port- 
land cement to be of approved make and to meet such tests as the engineer 
may prescribe. Sand to be clean and sharp and of approved quality. Con- 
crete will be laid in layers of not over 6 inches thick and thoroughly rammed 
if so directed. Pockets for generator leads shall be provided as directed. 



STEAM POWER PLANTS 87 

The top of foundation to be of such a height that the tile floor of the engine 
room can be laid over it and touch the base of the engine and generator. The 
generator pit shall be provided with curb angles with mitered corners properly- 
secured into foundations so that tile may be laid flush with and against it. 
The generator pit shall be lined with white tile by the tile contractor. The 
engine contractor shall furnish substantial board templates for building the 
foundations. 

When the engine and generator are set and blocked up on wedges, the con- 
tractor for the foundation will build a suitable dam around the edges of the 
engine bed and support for the generator, and he shall then supply and com- 
pletely fill with grout the voids between the engine bed and the foundation 
and the space between the foundation bolts and inclosing pipes. Grout shall 
consist of one part Portland cement and one part sand with sufficient water to 
make a fluid substance. Particular care shall be taken before the grouting 
is commenced that the foundation bolts extend up through the foundation 
only by such a distance as will be required by a full nut. 

Within thirty days after the engine and generator contracts are let the 
engine builder shall submit foundation drawings for approval, to be not less 
than scale of | inch to the foot. The engine builder shall be responsible for 
the accuracy of the drawings of the foundations for the engines and generators. 
He shall furnish anything needed at the proper time to prevent delay. 

Each bidder shall furnish with his proposal the allowance he will make 
from his bed provided the owners construct the foundations and do the grout- 
ing and setting of curb angles. 

Foundation Bolts. — A complete set of foundation bolts, machine-finished 
nuts, and all necessary anchor plates and pipes must be furnished. Anchor 
plates shall be so made as to prevent lower nut on foundation bolt from turn- 
ing. A steel pipe of proper length and of a diameter about 2 inches larger 
than the diameter of the bolts shall be furnished with each foundation bolt. 

Bolts and Nuts. — Case-hardened and finished polished nuts shall be used 
in all exposed work, and also for all parts requiring frequent removal and 
adjustment. All other nuts and bolt heads above the floor level shall be 
finished. All nuts in contact with polished surfaces shall be polished. 

All nuts and bolt heads shall be hexagonal in shape and must be faced on 
top and bottom at right angles to the axis of the bolt. The sides of all nuts 
shall accurately fit corresponding wrenches. All nuts of pillow-block cap 
bolts and follower bolts of pistons, all screw joints in moving parts, and all 
keys shall be provided with a secure locking device. Through bolts shall be 
used in preference to studs wherever practicable. 

Workmanship. — All fits shall be thoroughly machined. No shims will be per- 
mitted. No file fits will be allowed in the construction. Polished surfaces are to 
show no tool marks. All nuts on rough castings shall fit facings raised above the 
surface, except where otherwise directed. All flanges, collars, and offsets shall 
have well-rounded fillets. All unfinished surfaces shall be smooth, devoid of all 
imperfections, chipping, or other rough tool marks, and shall be properly cleaned, 
rubbed, etc.; at all joints the pieces joined shall be made symmetrical and shall 
be dressed so as to match properly and present a neat finished appearance. Ail 
bolted joints shall be ream-bolted. All rotating or reciprocating parts shall 



88 STEAM POWER PLANTS 

be perfectly balanced when possible. All bright parts shall be carefully pol- 
ished and then slushed before shipment with white lead and tallow. After 
erection they shall be thoroughly cleaned. No joints made by fracture will 
be permitted at any point. All valve rods, eccentric rods, stub ends, etc., 
shall have a polished finish. Throttle-valve spindles shall be polished all over 
and shall have polished hand wheels. All valves must be capable of being 
packed while open and under pressure. All machine work shall be made 
according to the interchangeable system, and all surfaces which can be advan- 
tageously finished by wet emery grinding shall be so treated. No shrunk fits 
shall be used on any part. All pipes shall be full- weight standard. " All 
fittings for steam pipes shall be extra-heavy flanged. All castings must have 
good-sized fillets at all reentering corners, and the use of small brackets to 
stay flanges to the body of the casting will not be allowed. All flat surfaces 
and surfaces acted upon by pressure shall be substantially strengthened and 
stiffened with heavy ribs to make them of ample stiffness and strength to 
safely carry the loads to which they will be subjected. 

Attendant. — A competent attendant must be furnished by the contractor 
to take charge of the engines at the time of the trial run. He shall remain in 
charge and be responsible for the engines until same have been accepted. He 
must be qualified and will be required to give to the chief engineer all necessary 
and proper directions regarding the operation of the engines and other appa- 
ratus supplied under this contract. 

Test. — The engineer will make such proper tests as he deems necessary 
to find out if the engines and generators comply with the requirements of their 
respective specifications. Such tests will be made as soon as possible after 
the entire electrical and steam equipment is in a condition to test and a proper 
load can be obtained. The test will not be made, however, until the entire 
electrical equipment has been in regular and successful operation in a manner 
that is satisfactory to the engineer for at least one month, this period consti- 
tuting the trial run referred to in the preceding article. During the trial run 
and tests the contractor for this work shall cooperate with the contractor for 
other parts of the work, and he shall give the engineer such assistance as he 
may require. 

The friction load during the test shall be obtained by running the engine 
at its rated speed with a steam pressure of not less than 125 pounds, with the 
brushes of the generator not in contact with the commutator and the fields 
unexcited. 

Guarantees. — The contractor shall guarantee to furnish engines that shall 
run so easily that no vibration will be noticeable in any part of the building; 
that shall operate perfectly, without abnormal wear, without heating, and 
without objectionable noise. The contractor shall guarantee to make good 
any defect in workmanship or material or defect of any kind that may occur 
within one year of the date of acceptance of his work. 



j I Coal Vault. 1 r" 




Discharge Tunnel. 



Discharge Ti/nneh 





r >. 


\ 


\V^ 




"• •- ^a. Ss 








X-f^ 



C 8" 16' 24' 5Z 4ff 48' 



Plate 9. — Plan, Waterside Station, New York Edison Company. 

JOHN VAN VLECK, CONSTRUCTING ENGINEER. 



CHAPTER VI. 
TURBINES. 

Advantages of Turbines. — The steam turbine has reached such 
a stage of development that in many cases it is superior to 
the steam engine, particularly in situations where high rotative 
speeds may be employed, such as the driving of alternating- 
current electrical generators, centrifugal pumps, blowers, and 
compressors. Turbines driving direct-current generators up to 
700 kilowatts capacity that will give excellent satisfaction can be 
obtained, the earlier difficulties of commutation in the genera- 
tor having been overcome. The particular points of advantage 
of the steam turbine are high efficiency under variation in load, 
simplicity, economy of space, the absence of oil in the exhaust 
steam, the ease with which alternators driven by steam turbines 
may be operated in parallel, and the slight falling off in efficiency 
due to use. 

Attention. — There is no doubt but the turbine requires less 
attention than the reciprocating engine. There are few rubbing 
surfaces outside of the main bearings, and with these properly 
designed and lubricated the problem of looking after a turbine 
is a simple one. 

Space Conditions. — As to the economy of space due to the 
use of a turbine in place of an engine, this feature holds true to 
a greater extent with large units than it does with small ones 
if the maximum economy of each type of prime mover is to be 
obtained. A reciprocating engine of an economical type will 
be more efficient than a steam turbine if moderate steam pres- 
sures and moderate vacua are employed, as with turbines the 
steam must expand through a high range of pressure if it is 
to work economically. Where from 26 to 27 inches of vacuum 
have been common with reciprocating engines a vacuum of from 
28 to 28J inches is desired for steam turbines, and this high 
vacuum can only be obtained by using more expensive and 
more elaborate condensing plants than would be required for the 

89 



90 STEAM POWER PLANTS 

lesser vacuum used with steam engines. Such condensing plants 
naturally take up a good deal of space, and where small turbines 
or even turbines of moderate size with such condensing plants 
are used it is doubtful if there is any saving of space due to the 
use of a turbine over that required by a steam engine with its 
condenser. There is one point in favor of the turbines, and that 
is they require less expensive foundations. One type of vertical 
turbine is now made for very large plants with the surface con- 
denser forming the turbine base. It is interesting to note in 
this connection that during the year 1911 the New York Edison 
Company replaced the 3500-kw. units driven by three-cylin- 
der compound engines installed in the Waterside Station No. 1 
by vertical turbines of 20,000 kilowatts capacity each. The 
actual floor area occupied by the engine-driven unit was 918 
square feet and by the turbine 297.5 square feet, so that the 
replacement will permit the development of six times the power 
in one-third of the space. It is interesting to note, in passing, 
that the steam consumption of the engine-driven units, while 
running at a speed of 73 r.p.m. with a steam pressure at the 
throttle of 185.6 pounds with a vacuum of 27.25 inches, while in- 
dicating 5442 horse-power, amounted to 11.93 pounds per horse- 
power per hour and 16.74 pounds of steam per kilowatt hour. 
The turbines replacing them are designed to operate with a 
steam pressure of 175 pounds and a vacuum of 28 J inches and 
with steam superheated 100 degrees. Under these conditions 
they are guaranteed to operate with a steam consumption of 
15 pounds per kilowatt hour when developing 20,000 kilowatts, 
14.4 pounds when developing 15,000 kilowatts, and 15.0 pounds 
when developing 10,000 kilowatts. Even when allowing for the 
more favorable conditions as to superheat and vacuum in the 
turbine, the turbine has somewhat the best of it in so far as 
economy is concerned. 

Absence of Oil. — The absence of oil in exhaust steam from 
turbines makes their use advisable where exhaust steam free 
from oil may be used for some manufacturing purpose. It is 
also a decided advantage in eliminating the troubles due to oil in 
boiler-feed water where a surface condenser is used permitting 
the water to be used over and over again. 

Overload Capacity. — The unusual overload capacity of a 
steam turbine, which is often referred to as being of particular 



STEAM POWER PLANTS 91 

merit, depends entirely upon the rating of the turbine and of the 
generator to which it is connected, if it is an electrical generating 
unit. With a steam engine as ordinarily proportioned the point 
at which the engine speed begins to fall off to such an extent as to 
be troublesome is usually at overloads of from one-third to one- 
half of its rated capacity. There is no reason, however, why the 
cylinders cannot be made so as to withstand still greater over- 
loads if the electric generator is built to stand it. 

Variable Loads. — The steam consumption of a turbine, or at 
least some turbines, varies less at partial loads or at overload 
than it does with reciprocating engines, as will be seen by an 
examination of the data upon both types of prime movers under 
varying loads given in this volume. 

Durability. — The indications are that a turbine, if properly 
constructed, is less affected by use, in so fa*r as its steam con- 
sumption is concerned, than is the reciprocating engine, where 
the rubbing of the valves and piston will cause piston and valve 
leakage that will affect the economy to a varying extent depend- 
ing upon the amount of wear. Wear does occur in buckets of 
some turbines, particularly when moisture is present in the steam. 
While it is believed that with superheated steam and properly 
made buckets the wear is negligible, it may be too soon to say 
that no wear occurs. 

Relative Operating Costs. — Some interesting data given in 
Table 14 was furnished by Mr. Henry G. Scott, chief engineer 
of the Interborough Rapid Transit Company in New York City, 
an engineer of large experience in large power-house operations, 
in the Proc. Am. Inst. Elec. Engrs. in 1906, bearing upon the 
relative cost of operation with turbines and with reciprocating 
engines for street railway power houses of large size. 

Table 15 shows the steam consumption per kilowatt hour that 
might be expected from electrical generators connected to various 
types of steam engines and to steam turbines. 

Steam superheated 125° F. 

The chances are that a well-designed Corliss engine driven unit 
of large size will operate quite as economically as a steam turbine 
of equal capacity when operating under conditions equally favor- 
able to both. 



92 



STEAM POWER PLANTS 



TABLE 14. — RELATIVE COST OF OPERATION OF TURBINES 

AND ENGINES. 



Maintenance. 


Reciprocating 
engine. 


Steam turbine. 


1. Engine room, mechanical 

2. Boiler room 


2.57 
4.61 
0.58 
1.12 

2.26 
1.05 
0.74 
7.15 
0.17 
61.30 
7.14 
6.71 
1.77 
0.30 
2.52 

100 

100 


0.51 
4.30 
0.54 
1.12 

2.11 

0.94 

0.74 

6.68 

0.17 

57.30 

0.71 

1.35 

0.35 

0.30 

2.52 

79.64 

82.50 


3. Coal- and ash-handling apparatus 

4. Electrical apparatus 

Operation. 

5. Coal- and ash-handling labor 

6. Removal of ashes 


7. Dock rental 


8. Boiler-room labor 

9. Boiler-room oil, waste, etc 

10. Coal 

11. Water 

12. Engine-room mechanical labor 


13. Lubrication 


14. Waste, etc 

15. Electrical labor 


Relative cost of maintenance and operation . . . 
Relative investment, per cent 



TABLE 15. — PROBABLE STEAM CONSUMPTION OF ENGINES 

AND TURBINES. 





Steam pressure, 

pounds by 

gauge. 


Vacuum, inches. 


Pounds of 
steam per kilo- 
watt hour. 


High-speed compound engine .... 

100-kw. turbine 

High-speed compound engine 
High-speed compound engine .... 

Corliss simple engine 

Corliss simple engine 

Corliss compound engine 

Corliss compound engine 

100-kw. turbine 

500-kw. turbine 

5000-kw. turbine 


90 
150 
150 
150 
100 
100 
150 
150 
150 
175 
175 





26 


26 


26 
27 
28 
28 


48 
50 
36 
30 
39 
32 
30 
20 
32 
20 
16 



Effect of Vacuum and Steam Pressure. — With turbines of 
about 300 kilowatts capacity with a steam pressure of 150 pounds 
by gauge, a steam consumption of about 50 pounds per kilowatt 
hour might be expected if run noncondensing with a back pres- 
sure equivalent to the pressure of the atmosphere. With a back 
pressure of about 5 pounds by gauge there would be an in- 






STEAM POWER PLANTS 



93 



crease of about 10 per cent in the steam consumption. With the 
same turbine when exhausting into a vacuum of 28 inches, the 
steam consumption would be about 25 pounds per kilowatt hour. 

As to the effect of varying the vacuum, steam pressure, and 
superheat in turbine work with a steam pressure of 175 pounds 
by gauge, there is an increase in the energy available in the 
steam of about 5 per cent by increasing the vacuum from 28 
to 28^ inches. The gain due to an increase in steam pressure 
amounts to about 1 per cent for every 10 pounds increase in 
pressure at an expense of about one-tenth of 1 per cent in the 
total heat in the steam for every 10 pounds increase. 

The superheating of steam 100° F. with a steam pressure of 
175 pounds by gauge and with a vacuum of 28 inches increases 
the total heat supplied to the steam by about 4J per cent, with a 
corresponding reduction in the steam consumption of the turbine 
of about 8 per cent, resulting in a net gain of about 3 \ per cent. 



TABLE 16.— ECONOMY TESTS OF STEAM TURBINES. 



Turbine. 



Rummelsburg, A. E. G 

Carville, Parsons 

Chicago, Curtis 

Berlin Moabit, A. E. G 

Boston, Curtis 

City Electric, San Francisco, 

Westinghouse 

N. Y. E., Westinghouse 

Brown-Boveri, Rhenish West- 

falen 

N. Y. E., Curtis 

Pacific Curtis, Oakland 



Load, 
kilowatt. 



Steam 
pres- 
sure, 

pounds 
abso- 
lute. 



4,179 
5,164 
10,816 
3,150 
5,195 

8,563 
9,830 

5,128 

8,880 
8,775 



179 
207 
190 
185 
179.5 

183 
192.2 



Super- 
heat. 



289.3 

125.2 

147 

225 

142 

59 
96 



176 193.7 
192.5 108.5 
194 72.95 



Vacu- 



29.19 

29 

29.47 

28.5 
28.8 

28.18 
27.31 

28.47 

28.1 

28.03 



Steam, 
pound 
per 
kilo- 
watt 
hour. 



11.95 

13.15 

12.9 

13 

13.52 

14.427 
15.15 

14.32 
15.05 
15.95 



B.t.u. 
per kilo- 
watt 
hour. 



15,665 
16.122 
16,206 
16,352 
16,578 

16,850 

17,778 

17,790 
17,940 
18,735 



Some interesting data upon the performance of turbines of 
large size were given by Mr. George A. Orrok in the Transactions 
of the American Society of Mechanical Engineers for 1910. They 
are contained in Table 16. The different turbines are operating 
under different conditions as to pressure, superheat, and vacuum, 
and therefore cannot be compared one with the other without 
taking these factors into consideration. 



94 



STEAM POWER PLANTS 



In a test of a 10,000-kw. normal-rating Westinghouse turbine 
by Mr. S. L. Naphtaly, in March, 1910, at the City Electric 
Company in San Francisco, the results given in Table 17 were 
obtained: 



TABLE 17. — TEST OF WESTINGHOUSE TURBINE IN SAN 

FRANCISCO. 



Load in kilo- 
watts. 


Steam 
pressure. 


Superheat, 
degrees Fah- 
renheit. 


Vacuum, 
30-inches par. 


Water per kilo- 
watt hour. 


Steam per kilo- 
watt hour. * 


5333 

7972 
8198 
9173 


173 
171 

169 
167 


54 
58 
60 
59 


28.34 
28.28 
28.10 
27.90 


15.65 
14.58 
14.59 
14.57 


15.21 
14.11 
14.04 

13.88 



* Corrected to 175 pounds steam pressure, 100 degrees of superheat, and 28 inches of vacuum. 

Some additional data upon the steam consumption of small 
turbines at various loads will be found in the specifications for 
turbines. 

Exhaust-steam Turbines. — By connecting a turbine to the 
exhaust of a noncondensing engine and supplying the turbine 
with a condenser so that it may operate condensing, the power 
that may be obtained from the same amount of steam may be 
increased very materially. While this may also be accomplished 
by attaching a condenser direct to the steam engine, there is the 
probability of obtaining greater capacity by expanding the steam 
through the lower stages in a turbine than in a steam engine, 
for the reason that cylinder condensation limits the number of 
expansions that it is advisable to use in a steam engine to about 
36, while the number of expansions that is possible to obtain with 
a turbine is limited only by the cost of the condensing equipment 
necessary to obtain them. 

Specifications. The following has been slightly condensed 
from a specification for small turbine generating sets for use on 
ship-board by the United States Navy Department. 

Each set to consist of an electric generator driven by a steam turbine, both 
mounted upon a common bed plate, or having a common frame provided 
with ample supporting feet. To be complete with throttle valve, and for sets 
mounted upon a common bed plate to be fitted with bosses for hand-rail 
stanchions. 

The set as a whole shall be as compact and light as is consistent with due 
regard to strength, durability, and efficiency. The maximum allowable normal 



STEAM POWER PLANTS 



95 



speed, weight, over-all dimensions, and end clearance for disassembling to be 
as shown in Table 18. 

TABLE 18. 



Kilo- 
watt. 


Revo- 
lutions 

per 
minute. 


Length 
over 
all. 


Base 
width. 


Height 
over 
all. 


Width over 
pipe con- 
nections. 


Clearance for assembly. 

r~ Turbine Co ™~ 

Top - end muta " 
tor end. 


Weight in 
pounds. 


5 
10 

25 

50 
100 
200 
300 


5000 
4500 
3600 
3300 
2400 
1700 
1500 


Inches. 

52 

60 

90 
100 
130 
174 
175 


Inches. 

18i- 

21 

32 

39 

62 

76 

76 


Inches. 

28 
30 
40 
51 
82 
92 
92 


Inches. 

25 

30 

40 

47| 

72 
100 
100 


Inches. 

5 
10 
10 
13 
13 


Inches. 

3 
5 
6 
6 
6 
6 
6 


Inches. 

5 

3 
3 


950 

1,650 

4,300 

9,500 

17,500 

29,000 

31,000 



The design shall provide for accessibility to all parts requiring inspec- 
tion during operation, or adjustment when under repair. Sets of 100-kw. 
capacity and larger shall be provided with coupling between the armature 
and turbine wheels to permit the removal of the armature without disassem- 
bling the turbine. Only sets with turbine directly connected to the generator 
will be approved. 

The set must be capable of running without undue noise, excessive wear or 
heating; must be balanced and run true at all loads, up to 33| per cent above 
rating; and must be capable of running for long periods under full load. 

Cast or wrought iron shall not be used for bearing surfaces. Both upper 
and lower halves of main bearings are to be removable without removal or 
displacement of shaft, on sizes of 50 kilowatts and over. 

Suitable thrust bearings will be provided to prevent such movement of 
the shaft in direction of its length as might be caused by pitching of the ship 
with set erected with its shaft extending fore and aft. 

The bed plates, where used, to be a substantial casting provided with 
accurately spaced, drilled holes for securing to foundation, and with lugs for 
securing hand-rail stanchions. 

The seats for all bolt heads and nuts to be faced. All external nuts subject 
to frequent use to be case-hardened, and all nuts to be United States standard 
size. Where liable to work loose from vibration, nuts to be securely locked. 
All bolt ends to be neatly finished. 

Adjoining portions of the machinery, where efficiency and good operation 
are affected by alignment, shall be doweled or rabbeted together, dowels to 
be fitted to accurately reamed holes. Through dowels in all cases to be pro- 
vided with threads and a nut for withdrawal. Adjoining portions of the 
machinery shall be given corresponding marks, when desirable for insuring 
correct assembly. 

Necessary wrenches, lifting eyes, jacking-off bolts for removing wheels, 
and all special tools, feelers, etc., required for assembling and disassembling 
the set to be furnished, mounted on a board, suitable for mounting on bulkhead. 

Interchangeability among the different sets and their spare parts, of the 



96 STEAM POWER PLANTS 

same size and make, as furnished in any one contract, is required. This is to 
be demonstrated as part of the final test for acceptance. 

The general appearance of the set resulting from design and workmanship 
must be of the highest character. Any defect not caused by misuse or neglect, 
which may develop within the first six months of service, to be made good, by 
and at the expense of the contractor. 

The works in which the construction of the machines is being carried on 
shall be open at all times during working hours to the inspecting officer and 
his assistants. Every facility shall be given such inspectors for the proper 
execution of their work. 

The contractor shall make, at his own expense and previous to delivery, 
sufficient tests to insure that the sets conform in all respects to the specifica- 
tions. 

To prevent delays and additional cost to the Government of repeated tests, 
no more than two tests will be made after delivery of the set, the second test 
to be made within such time after the first test as may be stipulated by the 
Government. Failure to make the necessary repairs or remedy defects within 
that time will be cause for final rejection of the set. If left upon Government 
property while undergoing repairs, the risk of loss by fire will be the contractors. 

It is the intention of these specifications to produce a generating set which 
shall be first-class in every particular relating to design, construction, or opera- 
tion. Any omission from these specifications of any part of the machinery 
necessary to produce above results, or failure to describe design and con- 
struction of same, shall not operate to release the contractor from supplying 
such part of the machinery or from performing such work as part of the con- 
tract, and without additional expense to the Government. 

The contractor shall forever protect and defend the United States in the 
full and free use and enjoyment of any and all rights to any invention or 
device which may be used in the construction, or whose use may be required 
for the successful operation of the generator sets, against any and all persons 
or corporations. 

Turbine. 

The turbine shall be of the horizontal type, designed to ordinarily run 
condensing, but capable of operating at full load noncondensing with 5 pounds 
back pressure. The turbine to be of sufficient power when running condens- 
ing to drive the generator for an indefinite period at rated speed when the 
generator is carrying If load. 

With normal steam pressure of 200 pqunds, dry saturated steam, the steam 
consumption for \, f, 1, and If loads shall not exceed the amounts given 
in Table 19. 

Superheating may be employed to insure dry steam, a proper correction 
being applied to the water rate to compensate for the degree used. 

On all turbines operating condensing, the valve gear shall work automati- 
cally over the total range of conditions without adjustment of hand valves 
or similar devices. The words "total range of conditions" shall be inter- 
preted to mean operation from zero to full load condensing, when operating 
with normal steam pressure and minimum vacuum of 23 inches. For over- 
load and noncondensing operation, sets may be equipped with one hand valve. 



' 



* 




Plate io. — Cross Section, Waterside Station, New York Edison Company. 



STEAM POWER PLANTS 



97 



TABLE 19. — WATER CONSUMPTION. 



Rated 
kilowatt. 


Kilowatt 
load. 


Vacuum. 


28 inches. 


27 inches. 


26 inches. 


25 inches. 


5 


3 

4.5 
6 

8 


87.75 
68.25 
56.00 
50.50 


88.25 
68.50 
56.50 
50.75 


89.00 
69.00 
56.50 
51.00 


89.50 
69.25 
57.00 
51.50 


10 


6 

9 

12 

16 


60.50 
49.25 
44.25 
41.25 


64.75 
52.00 
46.25 
42.25 


68.50 
54.50 
48.50 
43.25 


73.00 
58.00 
52.00 
45.00 


25 


15 

22.5 
30 
40 


54.75 
45.75 
40.00 
38.25 


55.50 
46.50 
40.25 
39.00 


56.25 
47.00 
40.50 
39.50 


57.50 
48.50 
42.00 
41.00 


50 


30 
45 
60 

80 


37.75 
32.00 
29.25 
26.75 


40.00 
34.00 
31.00 
28.50 


42.50 
35.50 

32.75 
30.00 


45.00 
37.00 
34.50 
31.50 


100 


50 

75 
100 
133.3 


36.00 
31.00 
28.00 
28.00 


38.75 
33.50 
29.50 
29.50 


41.50 
35.50 
31.00 

30.75 


44.00 
38.00 
33.00 
32.00 


200 


100 
150 
200 
266.6 


36.25 
30.50 
26.50 
26.50 


39.00 
32.50 
28.00 
28.00 


41.50 
35.00 
29.75 
29.50 


43.00 
36.00 
32.00 
31.00 


300 


150 
225 
300 
400 


31.00 
27.50 
25.50 
26.50 


33.25 
29.25 
26.75 
27.00 


35.50 
31.00 
28.00 
28.50 


36.50 
32.00 
29.50 
30.00 



Buckets and reversing vanes shall be of material which will not injuriously 
rust or corrode under the action of steam. 

The turbine to run smoothly and furnish the required power for full load at 
any steam pressure within 20 per cent (above or below) of those given in the 
table, and exhausting to condenser at 25 inches of vacuum; to furnish power 
for 90 per cent of full load at steam pressure 20 per cent below normal, and for 
full load at any steam pressure between normal and 20 per cent above normal, 
when exhausting into the atmosphere. It shall bear without injury the sud- 
den throwing on or off of one and one-third times the rated load of the genera- 
tor by making and breaking the generator's external circuit. 

Turbine to have steam flanges on the right or left side, and exhaust flanges 
at bottom pointing down, or at bottom pointing to right or left, as may be 



98 STEAM POWER PLANTS 

specified for the different installations. All piping shall be supported at 
points close to the turbine so as not to affect the alignment of parts or cause 
undue strain in turbine casing. 

The steam inlet to be fitted with throttle and emergency valves (combined 
in one valve, if preferred) equipped with strainer intervening between the 
valves and the steam line. The emergency valve will be connected to the 
emergency governor in such a way that it will automatically close between 
7 per cent and 10 per cent above normal speed of the turbine. Valve flange 
drilling to conform to specifications of the Bureau of Steam Engineering. 

The governor shall be of the centrifugal or inertia type, designed to regulate 
the speed within specified limits. 

Lagging shall be fitted as extensively as practicable to the turbine. It 
shall be done after preliminary acceptance of the turbine, in order that any 
defects in casting or joints may be readily found. The arrangement for 
securing the lagging in place shall admit of its ready removal, repair, and 
replacement. 

The speed variation will not exceed 2\ per cent, when load is varied between 
full load to 20 per cent of full load gradually, or in one stop, turbine running 
with normal steam pressure and vacuum. A variation of not more than Z\ 
per cent will be allowed when full load is suddenly thrown on or off the genera- 
tor with steam pressure constant between normal and 20 per cent above nor- 
mal, a variation of not more than 3| per cent when 90 per cent of full load is 
suddenly thrown on or off the generator with constant steam pressure at 
20 per cent below normal, exhausting in both cases either into a condenser or 
the atmosphere. No adjustment of the governor or throttle valve during the 
tests shall be necessary to insure proper performance under the above con- 
ditions. 

The turbine will operate without the use of lubricants in the steam spaces. 
Forced lubrication will be used on all bearings on which the shaft pressure 
exceeds 20 pounds per square inch of projected bearing surface. In case of 
forced lubrication, bearings to be cooled by water circulating in coils. These 
coils to be connected to the water system outside the pedestal. 

Mandrels, with collars, complete, will be furnished for renewing the white 
metal of all bearings so fitted. 

The material and design of the turbine will be such as to safely withstand 
all strains induced by operation at the maximum steam pressure specified, and 
by tests noted below. 

The following shall be provided with each set as indicated: 
(a) One 6-inch brass combination gauge for exhaust casing, graduated 
30 inches vacuum and 30 pounds pressure. 

(6) Two 4^-inch steam seal gauges, 30 pounds scale. 

(c) Where forced lubrication is used, one 4|-inch oil pressure gauge to be 
furnished at the pump, and on sets of 200 kilowatts and above; a gauge also 
to be furnished for each bearing. 

(d) An automatic device shall be installed on the turbine which shall shut 
off the steam by closing the throttle or emergency valve when the back pres- 
sure in the exhaust casing reaches between 10 and 15 pounds per square inch. 
The device to be so designed as not to be liable to impair the vacuum, and 



STEAM POWER PLANTS 99 

shall not be of a piston or other type, that may stick, due to infrequent 
use. 

(e) A pop safety valve not larger than f I.P.S. exhausting to the atmos- 
phere, shall be fitted to the turbine, of size sufficient to prevent injurious 
back pressure, due to possible leakage of the throttle valve. 

(/) The assembled turbine shall stand a hydrostatic test of 50 pounds per 
square inch. 

(g) Sets of 50-kw. capacity and above to be provided with a permanently 
connected direct-reading tachometer. All sets to be so designed as to permit 
the use of a portable tachometer or counter to determine speed. 

(h) Where forced lubrication is used, provision to be made on the discharge 
side to permit the observation of the flow of oil and cooling water from each 
bearing. An adjustable relief valve to be supplied as part of the oil pump, 
which shall be of the rotary type. 

00 Oil tank, when employed, to be supplied with sight gauge and a f-inch 
bibcock at lowest point to permit withdrawal of water from the bottom of 
the tank. 

(j) Provision shall be made for mounting commutator truing device, one 
of which shall be supplied for generators. 

Generator. 

Generator to be of the direct-current compound-wound type, designed to 
run at constant speed and to furnish a pressure of 125 volts at the terminals, 
at rated speed with load varying between no load and one and one-third times 
rated load. 

J The magnet frame to be circular in form with inwardly projecting pole 
pieces. Sets of 50 kilowatts and above are to have the magnet frame divided 
horizontally, the two halves being secured with bolts to allow the upper half 
with its pole pieces and coils to be fitted to provide for inspection or removal 
of armature. The pole pieces shall be bolted to the frame. The magnet 
frame of sets with bed plate to be provided with feet of ample size to secure a 
firm footing. 

Facilities to be provided for vertical adjustment of the magnet frame of 
sets with bed plate. 

The laminations for the armature will be accurately punched from the 
best quality of thoroughly annealed electric sheet steel; slots to be punched 
in the periphery of the laminations to receive armature windings. The lami- 
nations will be insulated from each other and will be assembled on the spider 
or shaft and securely keyed. Laminations will be set up under pressure and 
held securely by end flanges. 

The commutator bars will be supported on the shaft so that no relative 
motion can take place between the windings and bars. The bars will be of 
hard drawn copper finished accurately to gauge. The insulation between 
bars will be of carefully selected mica of not less than 0.025 inch thick. The 
bars will line with the shaft and run true and will be securely held in place 
by means of clamping or shrink rings. 

The brushes will be composed of carbon. Each brush will be separately 
removable and adjustable without interfering with any of the others. The 



100 STEAM POWER PLANTS 

point of contact on the commutator will not shift by the wearing away of the 
brush. 

Brush holders to be staggered in order to even the wear over entire surface 
of commutator; the generator to be provided with provision which will permit 
shifting all the holders simultaneously. All insulating washers and bushings 
to be damp-proof and unaffected by temperature up to 100° C. 

Finished armature to be true and balanced both electrically and mechani- 
cally, and run smoothly and without vibration. The shaft to be provided 
with suitable means to prevent oil from bearings working along to armature. 

All copper wire to have a conductivity of not less than 98 per cent. 

The main field coils, and commutating coils, if any, respectively, of any 
one set to be identical in construction and dimensions, and to be readily re- 
movable from the pole pieces. The shunt coils as well as the series coils are to 
be connected in series. 

Connection boards will be mounted on the generator with necessary ter- 
minals for the main, equalizer, and shunt cables. Sets of 30 kilowatts and 
above to be provided with pilot lamp on the machine. 

The field rheostat to be of fireproof construction, suitable for mounting 
behind the switchboard unless otherwise specified; to be provided with a 
shaft projecting through to the front, either directly connected or by sprocket 
chain. Hand wheel for front of switchboard to be supplied and to be marked 
to indicate direction of rotation for raising and for lowering the voltage of 
generator. The total range of adjustment to be from 10 per cent above to 20 
per cent below rated voltage. Variation to be not more than \ volt per step 
at both full and half load. 

Operation of Generator. 

The compounding to be such that with turbine working within specified 
limits, field rheostats and brushes in a fixed position, and starting with normal 
voltage at no load or at full load, if the current be varied step by step from 
no load to full load, or from full load to no load, and back again, the difference 
between maximum observed voltage and minimum observed voltage shall not 
exceed 2\ volts. 

The compounding and heat run (full load and overload) of the generating 
sets must be made with identical brush positions. 

The dielectric strength for resistance to rupture shall be determined by a 
continued application of alternating E.M.F. of 1500 volts for one minute. 
Test of dielectric strength shall be made with the completely assembled ap- 
paratus and not with the individual parts, | and the voltage shall be applied 
between the electric circuits and surrounding conducting material. 

Insulation resistance shall be not less than one megohm. 

With brushes in a fixed position, there shail be no sparking when load is 
gradually increased or decreased between no load and full load ; no appreciable 
sparking when load is varied up to one and one-third times rated load; no 
detrimental sparking when one and one-third load is removed or applied in 
one stage. 

The temperature rise of the set after running continuously under full load 
for four hours must not exceed the following: 



STEAM POWER PLANTS 101 

Deg. C. 

Armature, by thermometer 40 

Commutator, thermometer 45 

Series field coils, by thermometer 40 

Shunt field coils, by resistance method 40 

Shunt rheostat, exposed surfaces, by thermometer 75 

Series shunt, by thermometer 40 

The jump in voltage must not exceed 15 per cent when full load is suddenly 
thrown on and off. 

The rise in temperature to be referred to a standard room temperature of 
25° C. Room temperatures to be measured by thermometers placed three 
feet from the generator so as to indicate the actual temperature of the room, 
but in no case to be within three feet of the turbine or other source of heat. 

The generator to be capable of satisfactory operation for a period of two 
hours, carrying one and one-third times its rated full load in a room tempera- 
ture of 35° C, under which condition the rise in temperature of no part shall 
exceed 60° C. 

With two or more generators of the same manufacture operating in parallel, 
each machine shall not vary above or below its proportion of load (l to If 
load) more than 12 per cent of its full-load normal current (provided the resist- 
ance of the line cables on the equalizer side of the machine terminals to the 
bus be such as to give within 10 per cent of equal drop in the cables of all 
machines, when carrying their respective normal currents) . This distribution 
of current is illustrated as follows : With any number of machines in multiple, 
each of 1000 amperes rated capacity, the difference between the average load 
upon all machines and the load carried by any one machine shall not exceed 
120 amperes or 12 per cent of the normal rating of the machine. 



CHAPTER VII. 
ARRANGEMENT OF STEAM AND WATER PIPING. 

Drawings. — After contracts have been let for the engines, 
boilers, pumps, feed-water heater, and other auxiliaries of a plant, 
the engineer should obtain accurate drawings or blue-prints of 
each, showing in plan and elevation the exact location of all steam 
and water inlets and outlets. When the engines, boilers, and 
auxiliaries are located finally upon the plans, accurate drawings of 
the piping to connect them should be made. The piping should 
be shown in plan and in at least one elevation. The drawings 
should be to a scale of at least J inch to the foot, and should show 
the location of every fitting and valve in the system. It saves 
time to indicate a valve by drawing correctly the position of its 
flanges and joining them by two crossed lines. When a number 
of fittings are to be placed close together, however, they should be 
drawn accurately and in full, for if this is not done it may happen 
that the piping cannot be put together on account of too much 
being crowded into the space allotted. An accurate drawing 
would prevent an error of this kind from occurring. Complete 
drawings result in lower bids, and do away with extras that are 
usually the result of incomplete or inaccurate drawings. 

Principles Involved. — The fundamental object to be accom- 
plished in steam piping is, of course, to carry steam without exces- 
sive loss of pressure; and next in importance is the requirement 
of safety, that the condensation loss shall be a minimum, and that 
the piping shall not leak. The greatest enemy to safety is the lia- 
bility of water entering the system, or collecting in it, due to con- 
densation; and it is, therefore, of particular importance that pip- 
ing should be so constructed that it does not contain pockets in 
which water can collect. Pipes are usually proportioned so that 
steam travels at the rate of about one mile a minute, hence if a 
" slug " of water, as a body of water is sometimes called, is picked 
up by the steam and carried along with it, an accident is very apt 
to occur, either by the rupture of an elbow, at a change in direc- 

102 



STEAM POWER PLANTS 103 

tion of the pipe, or by the water entering the engine cylinder and 
wrecking it. In some instances pockets cannot be entirely done 
away with, but where they do occur they should be properly 
drained. Straightway globe valves, except when the stems are in 
a horizontal position, should not be used in a steam pipe, as the 
valve seat acts like a dam in forming a water pocket. Valves 
of any kind, should never be placed so as to form a water pocket 
whether they are closed or open, if it is possible to locate them 
any other way. For instance, one frequently sees the stop valve 
on a boiler placed immediately above the boiler nozzle and a 
vertical section of pipe above the valve leading to an elbow 
from which a horizontal pipe leads to a steam main. When a 
boiler so connected is out of service, water due to condensation 
accumulates in the vertical pipe over the stop valve, and, although 
the pipe may be provided with a small drain pipe and valve, ex- 
perience has shown that the latter are not always made use of to 
draw off the water, so that an accident may occur. It is just as 
effective to use an angle stop valve at the top of the vertical pipe 
mentioned and to pitch the horizontal pipe that leads from it to 
the main so that condensation will flow toward the latter. With 
such an arrangement water cannot collect, and hence an oppor- 
tunity for an accident does not exist. 

Steam pipes should always be pitched so that the condensation 
that occurs in them will tend to flow in the direction in which the 
steam is moving, the reason for this being that if it is attempted 
to run condensation against the current of steam, water hammer 
is quite likely to occur, as the water accumulates into a slug, which 
is finally picked up by the steam and carried along until projected 
against a fitting. If one wants to carry, steam a long distance, 
from one point to another at a higher level, the pipe should be laid 
at the proper inclination, and at frequent intervals, say every 100 
or 150 feet, the line should drop a few feet into a pocket that can 
be drained through a steam trap into a small return pipe running 
back to the boilers. A horizontal pipe should be inclined so that 
the condensation will tend to flow against the current of steam 
only when the pipe is excessively large, so that the velocity of 
steam flow will be much below the usual practice. 

In systems of steam piping connecting several engines and the 
boilers supplying them, it is usually the custom to connect each 
boiler with a steam main from which pipes lead to the engines. 



104 STEAM POWER PLANTS 

p 

It is well to have this main of quite large size, so that the velocity 
of steam passing through it will be slow enough to allow any 
water that might be carried over from the boilers to accumulate 
in the main. The main, of course, should be drained by a pipe or 
pipes leading to a trap. If the main is divided into sections by 
valves, provision should be made for draining each section, for 
the reason that some parts may be shut off at times. Any branch 
to an engine should be connected to the top of the main to pre- 
vent, as far as possible, water from entering the branch. 

It is impossible to give definite information as to the design of 
piping for all steam plants, for the conditions met with vary so 
much. With electric power-house work, however, this is not the 
case, for the reason that the construction of these plants, unless 
they be very large ones, almost invariably follows one of two types 
that are standard as far as the relative location of engines and 
boilers is concerned. These types are as follows : that in which 
the boilers and engines are placed back to back, with a dividing 
wall between; and that with the boiler and engine rooms end to 
end, with the engines and boilers lying in the same direction. As 
far as the piping is concerned, the back-to-back type is the one 
most to be preferred, on account of the short and direct connec- 
tion between the engines and boilers and the ease with which it 
can be enlarged. With the engine and boiler rooms placed end to 
end the condensation losses in the steam piping are greater, and 
this type of station, as far as the piping is concerned, is not easily 
enlarged. Very large stations are usually arranged in units, with 
an engine or turbine placed opposite to and connected with as 
many boilers as are required to supply it. Cross connecting- 
pipes are used to connect the several units. 

The steam piping for that type of station in which the engines 
and boilers are placed back to back and separated by a wall 
usually consists of a feeder from each boiler, connected with a 
main which is supported by the boiler-room wall or suspended 
from the roof trusses and also connected to each engine. 

The engine-room floor is usually a little higher than that of the 
boiler room. The main and as much of the piping as possible 
should be located in the boiler room, for the reason that if an ex- 
plosion occurred in some section of the pipe in the boiler room, it 
would be possible after the steam pressure fell to cut out the dam- 
aged section and operate the rest of the plant. If the engine 





Discharqe Main from Condensers. Condenser 
3 Pumps., 

Longitudinal Section. 



Oft I Supply 
^'-^■J Basin. 



The Enqueuing RECORD. 





Jllfa^msfc^^^^V^ p^iU^ ^lw 



Longitudinal Section. 



l Enqj^ch.-o record 



Plan of Boiler Ro 



Tmi Ei.Q.KtEH.«a RECORD. 

Plate ii. — Power Station, Capital Traction Company, Washington, T>. C. 

D. S. CARLL, CHIEF ENGINEER. 



STEAM POWER PLANTS 



105 



| |* ,fe* >| I 




Packing. 



Expansion tee free exhaust main. 



BRACKET FOR STEAM MAIN. 




%%" 



H*M 




I i 

11 



If 

I 



SECTION STEAM MAIN. 



ANCHOR FOR STEAM MAIN. 



Fig. 23. Details of Steam Piping, Anderson Station (see Plate 6) . 
(Sargeant and Lundy, Engineers.) 



106 STEAM POWER PLANTS 

room, on the other hand, was the scene of the explosion and 
became filled with steam, the electrical apparatus would, in 
all probability, not be fit for service without considerable over- 
hauling. 

Two valves in a pipe leading from a boiler to a main are much 
more to be preferred than one, and are usually provided in large 
work. One should be close to the boiler, the other at the main. 
If there is only one, however, and the steam main is supported 
on a bracket on the boiler-room wall, it is a good arrangement 
to carry a pipe with a bend of long radius from the nozzle of 
each boiler to an angle stop valve bolted to a nozzle on the top 
of the main, as shown in Fig. 24, and to run a connection to each 
engine from a stop valve similarly located. Instead of the angle 
valve shown in the figure, an elbow with a gate valve adjacent 
to it, with the axis of the valve in a horizontal position, could be 
used. The valve in the pipe leading from the boiler to the main 
should not be placed over the boiler nozzle and thus form a 
pocket, for reasons previously explained. With both valves 
close to the main, they are easily reached from a light walk sus- 
pended from the roof trusses. Another advantage of placing 
the valve close to the main is that the condensation is less when 
the valve is closed. Some engineers prefer to place the angle stop 
valve immediately over the boiler nozzle and run a horizontal 
pipe from it to an elbow turning downward to a nozzle on the top 
of the main. The stop valve can then be reached by a person 
standing on top of the boiler setting. The engine connection 
should also be a bend of long radius. These connecting pipes 
will then have sufficient elasticity to permit expansion and con- 
traction to occur without injury to the pipe. With the arrange- 
ment suggested, there is no chance of water collecting in any part 
of the system, save in the main, and this should be large enough 
so that the water can settle there and pass out by the drain- 
pipes. Frequently the pipe leading to each engine is provided 
with a separator close to the throttle valve. Besides intercepting 
moisture in the steam, the separator performs another function 
of great value, in that it provides a reservoir of steam close to 
the cylinder, which insures a higher and more uniform pressure 
in the cylinder up to the point of cut-off than there would be if 
it were omitted; and it also reduces the vibrations in the steam 
piping due to the intermittent flow of steam as the valves of the 



STEAM POWER PLANTS 



107 



engine open and close. For these reasons a separator, particu- 
larly if of large volume, is of much value. 





Figure 24. 




Engine Cylinder 
eparator. 




Section A-B. 



Section C-D. 




Plan 



Fig. 25. 



Fig. 26. 



When the steam piping in the engine room is run in the base- 
ment, the arrangement shown in Fig. 25 can be resorted to. 
There the main is close to the floor of the boiler room. It can be 
supported on piers or wall brackets. The stop valve on the boil- 
ers is placed on the nozzle and a pipe with a long bend drops into 



108 STEAM POWER PLANTS 

the top of the main. The branch to each engine is run from an 
angle stop valve on the top of the main to a separator near each 
engine cylinder. This system is as unlikely to have accidents 
occur to it as is the arrangement shown in Fig. 24. An excellent 
example of this kind is shown in Plate 7. 

Sometimes the steam piping is put in in duplicate, the two sys- 
tems dividing at a double nozzle or Y on the boilers, and converg- 
ing at a similar Y close to and connecting with the throttle valve 
of the engine. Duplicate systems were used much more fre- 
quently in the early days of electric power-house construction 
than they are at the present time. In fact, the opinion is fast 
becoming universal that a duplicate system is an expense that 
is unnecessary with the arrangement of boilers and engines and 
piping shown in Fig. 24 or 25. 

It is the custom in the latest work to subdivide the power 
house into complete and independent units. The plans of the 
Lincoln Wharf power house of the Boston Elevated Railway 
in Plate 1 and Fig. 3 show how the piping is subdivided. By 
closing valves in the main each unit is entirely independent. 

If the power station has the engine and boiler rooms placed 
end to end, as in Fig. 26, the arrangement of piping shown there 
is probably the safest. It is arranged on the ring or loop system, 
and valves are so placed that if an accident occurs the damaged 
section may be cut out and the steam carried around through the 
system in the opposite direction. In the station shown an expan- 
sion joint is placed in the cross connection. The cross-over pipe 
might, perhaps, be omitted. In a station of any size the expan- 
sion in the mains running lengthwise of the engine and boiler 
rooms could be taken care of by anchoring the mains at their 
middle points, so that the expansion would be divided equally 
between the two ends of the mains. 

Exhaust Piping for Condensing Plants. — A frequent method 
of running exhaust pipes in condensing plants is shown in Fig. 
27. Each engine is supposed to be provided with an independent 
condenser and air pump. Two exhaust-pipe branches are shown, 
one branch dropping into the condenser and the other branch, 
which contains a relief valve, leading to the atmosphere. If ad- 
vantageous to do so, the free-exhaust pipes can be connected to 
a single pipe leading to the atmosphere. The purpose of the at- 
mospheric connection is to provide means for allowing the steam 



STEAM POWER PLANTS 



109 



to escape in case something happens to the condenser to prevent 
it from working. The relief valve is nothing more than a large 
check valve that is closed by the pressure of the atmosphere on 
one side, when a partial vacuum exists upon the other. Some- 
times several engines exhaust into one condenser. The general 
arrangement can be the same. Exhaust piping for condensing 
plants should have flanged fittings most carefully put together. 
A leak through a very small hole will greatly affect the vacuum 
and the efficiency of the engine. The principal point to be looked 
after is to have the alignment of the pipe such that there is abso- 
lutely no chance for water to lodge in the piping system, for the 
reason that the water might be sucked back in the engine cylinder 
and destroy it, as has frequently occurred. It is practically im- 
possible to drain the exhaust pipe of a condensing engine, except 
toward the condenser, as the system is under a partial vacuum. 
One of the most important points is to have very generously pro- 
portioned exhaust pipes with as direct a run to the condenser and 
as few bends in the pipe as possible. 




Fig. 27. 



Piping between Cylinders of Compound Engines. — It is some- 
times the custom in installing a cross-compound engine to arrange 
the piping between the cylinders so that high-pressure steam 
may be admitted to the low-pressure cylinder as well as the high- 
pressure, and to provide the necessary exhaust pipes so that both 
cylinders may be used at the same time as simple engines. If 
the engine is to be run condensing, it is sometimes so piped that 



110 



STEAM POWER PLANTS 



the high-pressure cylinder may run as a simple noncondensing 
engine, while the low-pressure cylinder may run as a simple con- 
densing or noncondensing engine, as may be desired. Designers 
have gone so far as to provide for running high-pressure cylinders 
as a simple condensing engine and the low-pressure cylinder as 
a simple noncondensing engine, although ordinarily intended to 
operate as an engine of the cross-compound condensing type. 
Various arrangements for accomplishing the purpose mentioned 
are shown in Plate 3 and in Fig. 18. 

Exhaust Piping for Noncondensing Plants. — In noncondens- 
ing plants the exhaust steam can be carried long distances for 
heating or for manufacturing purposes, provided the pipes carry- 
ing it are large enough. When exhaust steam is thus utilized, 
the pipe carrying the exhaust steam from the engines to the outer 
air, which is known as the atmospheric exhaust, or the free-ex- 
haust pipe, is provided with a back-pressure valve, the function 
of which is to preserve a sufficient pressure in the exhaust piping 
to cause the exhaust steam to flow through a system of pipes, 
also connected with this free-exhaust pipe, to the places where it 



lb Heating 

Syster 



D=Q1 




Boilers. 



O-JQ 



Q-Q 



Feed Water Heater Feed Water Main? 

[OH Separator {Exhaust Pipes. 



Injector' \ -t 



Ln Engine Ln 
IS- Cylinders. -AJ 



fresh Water 
Supply. 



Fig. 28. Exhaust and Feed Piping for Noncondensing Plant. 



is to be used. These back-pressure valves are designed so as to 
open when the pressure in the exhaust system exceeds a certain 
amount, and thus allow sufficient steam to escape to reduce the 
pressure to that desired. It sometimes happens, when exhaust 
steam is used for heating or for manufacturing purposes, that 
the supply is not sufficient to meet the demand, and if this is 
likely to occur, it is the custom to run a live-steam pipe from the 
high-pressure piping to the exhaust piping, and to place in this 



STEAM POWER PLANTS 



111 



connecting pipe a reducing valve which automatically opens and 
allows live steam to enter the exhaust system when the pressure 
in the latter falls below that which it is desired to maintain. 

When a system for utilizing exhaust steam is employed, it is 
frequently arranged in the manner shown in diagram by Fig. 
28. A grease separator should be provided to remove as much 
oil as possible from the exhaust steam, after which the steam is 
passed through the feed-water heater. The arrangement shown 
is designed for a feed-water heater of the closed type. From the 
heater the pipe branches, one branch supplying steam for heating 
or for a manufacturing purpose — this branch furnished with a 
high-pressure connection run from the boiler and containing a 
reducing valve. The other branch leads to the atmosphere, and 
it is provided with the back-pressure valve. The top of the free- 
exhaust pipe should have an exhaust head for intercepting the 
moisture that is blown out of the pipe by the exhaust steam. 
This head should have a drain pipe to a sewer or to waste. 

Most power plants have a basement under the floor of the en- 
gine room, and in steam plants for buildings the exhaust piping 
is frequently run in covered trenches. 
When the exhaust piping is below the 
floor, a satisfactory method of connect- 
ing the feed-water heater is shown in 
Fig. 29. The steam may pass through 
the heater or around it through the by- 
pass by properly adjusting the valves. 
It is quite common to connect a heater 
on the induction principle by pro- 
viding a single connection and rely- 
ing upon the pressure of the exhaust 
steam to fill the heater and drive out 
the air through a small air valve pro- 
vided for the purpose. The double 
connection to a heater is much to be 
preferred. 

Piping for Building Power Plants. - 




Fig. 29. 



Fig. 30 shows in dia- 
grammatic form the principal piping in a building containing 
about 900 horse-power in boilers for which the writer acted as 
consulting engineer for the steam work, and is typical of other 
installations. High-pressure steam is supplied to three engines 



112 



STEAM POWER PLANTS 



driving the electrical generators, to two boiler feed pumps, to 
three vacuum pumps, to three drip pumps, to two house-tank 
pumps, to a compressor for a refrigerating plant, to kitchen 
utensils requiring steam, and to the heating system. 



re 



Boiler 



rr\ 



y 



Engine 



Engine 




Make-up> 
Water Connecti 
Vent to Ati 



ion. TankT 
mosphere.-^i 



Keturn Heating System. 
Eeturn Temp'g Coils.- 



Vent 



aqk! 



Low Press 
Drip Tank 



$ 



Low P. Drip and Blow-off 
Tank Pumps. 



Fig. 30. 



There are two valves in the connection to each boiler also in 
the connection to each engine and pump. The valves on the 
boilers are of the automatic stop-and-check pattern which will 
close when an excessive flow out of the boilers due to a break in 
the steam-distributing system occurs, also when a break occurs 
in the boiler causing a flow of steam in the reverse direction, i.e., 
from the main into the boilers. To prevent water from entering 
the engine cylinders and to prevent vibration due to the inter- 
mittent flow of steam to the engines a receiver about 10 feet 




Plate 12. — Power Plant, Pittsburg and Lake Erie Railroad, Pittsburg, Pa. 

J. .A. ATWOOD, CH. ENG'R; WESTINGHOUSE, CHURCH, KERR & CO., ENG'RS AND CONT'RS. 



STEAM POWER PLANTS 113 

long and 3 feet in diameter is placed in the engine room and from 
this a separate branch is run to each engine. It would have 
been preferable to have placed a separate receiver on the cylinder 
of each engine, but the limited head room in the engine room 
prevented the use of a receiver of sufficient volume. 

The exhaust steam from all engines and pumps is collected 
in a main and then passed through a grease separator from which 
a free or atmospheric exhaust pipe runs to the roof. Close to 
the grease separator are branches from the exhaust main to the 
feed-water heater, to the hot-water generator, and to the heating 
system and between these connections and the atmosphere a 
back-pressure valve is placed in the exhaust main which can be 
adjusted to maintain any desired pressure on the exhaust main 
up to this valve, so as to force the steam into the heaters and 
into the heating system. The pressure in a well-designed system 
should not exceed from one to two pounds pressure above the 
atmosphere and a lower pressure should suffice where a vacuum 
heating system is used than would be required without it. 

The building is heated by direct radiation and a considerable 
volume of tempered air is supplied for ventilating purposes. 
Exhaust steam, supplemented by live steam through an auto- 
matically acting reducing valve, is used in the direct radiators 
and tempering coils; and to insure a thorough and noiseless cir- 
culation at low pressures, a vacuum system of heating is used; 
that is, vacuum pumps are attached to the returns from the 
heating system to suck the air and condensation from the system 
and maintain a slight vacuum on the return lines. This vacuum 
is maintained at a predetermined amount by means of a vacuum 
governor controlling the steam supply to the pumps. In this 
case the air tempering coils have a main return independent of 
return from the direct heating system and they are so piped that 
either return may be connected to any one of the three vacuum 
pumps, so that by having three pumps there will always be a 
spare pump should one break down. 

The boiler-feed pumps, of which there are two, draw water 
either from a main return tank, from the city supply direct, or 
from the water storage tank for the building, and force the water 
into the boilers either through the feed-water heater or direct. 
Either pump is sufficient in size so there is a spare pump. Both 
are governed by a pump governor of the float type attached to 



114 STEAM POWER PLANTS 

the return tank. In this plant, and in most others, the amount 
of steam exhausted by the engines and pumps is in excess of the 
amount of steam required to heat the building and this excess 
passes to the atmosphere by way of the free or atmospheric ex- 
haust. When this occ\irs it is manifest that the water returning 
from the heating system and the drips to the return tank will not 
be sufficient to supply the boilers, hence fresh water, or " make- 
up water " as it is called, is necessary. This is arranged for by 
running a cold-water pipe with valve in a convenient location 
in the boiler room to the return tank. Upon the opening of this 
valve by the boiler attendant the water level in the tank and 
governor, which are cross connected or equalized, rises so as to 
raise the float in the governor and so start the feed pump. The 
movement of the float up or down closes or opens a valve in the 
steam supply to the pump. 

The vacuum pumps and clean drips discharge into the return 
tank. The vacuum pumps for the heating system discharge 
more or less air and to relieve the return tank of all pressure 
a 4-inch vapor line running to the roof is provided. The drips 
running to the return tank consist of the condensation that oc- 
curs in the high-pressure mains, in the hot-water generator, in 
the steam separator, and in the feed-water heater. The grease 
separator is placed between the engines and the connections to 
the feed-water heater and the hot-water generator, and, as the 
grease separator may be out of use occasionally, means is pro- 
vided for turning all the high-pressure drips into the low-pressure 
or the dirty drip system. All drips from the high-pressure mains 
and branches are provided with traps ; also the feed-water heater 
and hot-water generator drips. The heater and hot-water gen- 
erators are set at such a level as to drain by gravity into the 
return tank. 

The low-pressure or dirty drips consist of drips in the exhaust 
mains and branches, grease separator, cylinder drains, etc., and 
these are run to a low-pressure drip tank which is about 3 by 
4 feet in size located in a pit so as to be well below the level of 
the lowest point to be drained. The tank is relieved of pressure 
by a 3-inch vapor line to the roof, and a pump controlled by a 
governor of the float type maintains a constant level in the drip 
tank and discharges into the main house sewer outside of the 
plumber's trap, this being done to prevent the vapor from the 



STEAM POWER PLANTS 115 

pump discharge from backing up into the house drainage system. 
Located in the same pit with the low-pressure drip tank is a 
blow-off tank into which the blow-off mains from the boilers 
connect. This is also vented to the roof by an independent pipe 
and is drained by a pump and governor also discharging into the 
sewer. In some cities an ordinance prohibits the discharge of 
steam or vapor-bearing water into the sewers and to overcome 
this it is customary to place within the blow-off tank and low- 
pressure drip tank a cooling coil of brass pipe through which the 
cold water supplied to the feed pumps is passed. 

While the plant shown in Fig. 30 and described above is typical 
of others there are many modifications of detail in practice. If 
an open type of feed-water heater is used the vacuum pumps 
would ordinarily be arranged to discharge into a separating tank 
perhaps 18 inches in diameter and 4 or 5 feet in length, and this 
would be vented to the atmosphere. The return tank would 
be omitted and the returns led directly into the feed-water 
heater near the bottom. The fresh water would be automatically 
supplied to the top of the heater by a float within. The sepa- 
rating tank would be elevated considerably above the heater, and 
it would be connected to the heater so that the water discharged 
by the vacuum pumps would pass from the separating tank to 
the heater by gravity. The pipe connecting them would con- 
tain what is known as a loop seal to prevent the exhaust steam 
in the heater from entering the separating tank and escaping to 
the atmosphere by way of the vapor pipe from this tank. The 
height of the column of water in the loop seal determines the 
maximum pressure therefore that can be carried in the heating 
system. 

Still one other method of piping exhaust-steam heating plants 
is to connect the returns from the direct-heating system into a 
return tank vented into the heating system drained by boiler- 
feed pumps perhaps with a governor with all high-pressure drips 
run to an independent tank pump and governor, the drip pump 
discharging into the feed main between the boiler-feed pumps 
and the governor. If a vacuum system of heating had not been 
used in the plant illustrated in Fig. 30, the returns from the 
direct-heating system could have been independently trapped 
into the return tank and the high-pressure drips as well, if the 
return tank was provided with a free vent to the atmosphere. 



116 STEAM POWER PLANTS 

Care of Drips. — The drainage from any part of the piping 
system is valuable on account of the value of the water, and the 
heat in the water that would be lost if the condensation was 
allowed to go to waste. By condensation is meant water due to 
condensation in the pipes. Sometimes the saving that is due to 
returning high-pressure condensation to the boilers is not suffi- 
cient to warrant the expenditure for the apparatus necessary to 
do this, but that is a point which must be determined for each 
case. Condensation from exhaust-steam pipes can sometimes 
well be allowed to go to waste, for the reason that it generally 
contains more or less oil; and the chance of this doing injury to 
the boilers is apt to be too great for the saving that would follow 
its utilization. If it is used, the water should be filtered or an 
efficient grease separator should be used. 

There are various methods of returning high-pressure conden- 
sation to the boilers, and the most common are the Holly system 
and the " steam loop," both patented systems controlled by 
Westinghouse, Church, Kerr & Company, by means of the auto- 
matically-governed steam pump and receiver and by means of a, 
return trap. With the pump and receiver all high-pressure drip 
pipes, from separators, steam jackets on the cylinders, from re- 
heating receivers placed between the cylinders of compound and 
triple-expansion engines, and all other points from which water 
is drained can be connected to a main leading to an automatic 
pump and receiver. Each drain pipe should have a steam trap, 
if there is any chance of their being under different pressures. 
The automatically-governed pump can discharge the water into 
the boiler-feed pipe between the boiler-feed pump and the boilers. 
With very long steam pipes which have to be drained at several 
points, the drainage can be drawn off by a steam trap discharg- 
ing into a return pipe leading to an automatic pump and receiver 
at the boiler house. If the inclination of the steam pipe is such 
that the water will not run back by gravity in the return pipe to 
the boiler house, the drip can be carried to the lowest point in the 
system and an automatic pump and receiver, operated by steam 
from the main pipe, can be located there and used to pump the 
water up hill and back to the boiler house; that is, of course, pro- 
vided the saving will warrant this arrangement. All high-pres- 
sure drip lines should be thoroughly covered with a nonconducting 
covering. 



STEAM POWER PLANTS 



117 



Low-pressure drips contain the condensation drawn from pipes 
carrying exhaust steam, steam condensed in feed-water heaters 
of the closed type, the drip from engine and pump cylinders, and 
the drip from grease separators. All of this condensation should 
be thrown away on account of the grease that it contains, unless 
some form of oil filter or an efficient grease separator is used. 
All low-pressure drips should be trapped independently into a 
drip main which can be led to any convenient place, such as the 
sewer, the pipe carrying off the discharge from the condenser, etc. 

Feed-water Piping. — Feed-water piping is sometimes put to- 
gether with screwed and sometimes with flanged fittings, and 
these are either of brass or cast iron. The pipe should be of brass, 
iron-pipe size. It is better to use elbows with a long radius to 
reduce friction or, what is better still, pipe bends of long radius 
wherever possible. Gate valves should be used instead of globe 
valves, for the same reason, excepting feed-controlling valves 
on boilers which should be of the globe type. 



Boilers. 



« 



O-O 



Check Valve. 
K$lobe Valve 



G^ 



Injector. 



Auxiliary Heater. - .>\ 

Hi 



By-Pass.- 



(^y^imaW) Hea+e((s) 



eS£ 



By-Pass. 







Feed I Pi/m vs 



<14zter. 



Hoi Well. 



Air Pump 

r Surface 
'Condenser 



~}AirPump 
\Cond 



J Air Pump 
\Cond 



Fig. 31. Feed Piping and Condensing Plant. 



An arrangement for feed-water piping for a typical plant 
equipped with surface condensers is shown in diagram by Fig. 
31. The plant is supposed to contain three engines, each with 
an independent air pump and surface condenser, two boiler-feed 
pumps, a primary heater in the exhaust pipe of each engine, be- 
tween the engine and surface condenser, and a single auxiliary 



118 STEAM POWER PLANTS 

heater of the closed type receiving the exhaust steam of the air 
pumps and the boiler-feed pumps. The steam condensed in each 
condenser is drawn therefrom by the air pumps and forced into 
a hot well, from which the boiler-feed pumps draw their supply. 
For occasionally replenishing the water from the condensers and 
supplying fresh water when needed, a fresh-water pipe is led to 
the hot well, and its supply can be controlled by a float valve or 
ball cock, so that fresh water will flow in the hot well in case the 
boiler-feed pumps draw water faster than it is discharged from 
the air pumps, an occurrence that is unlikely to happen. The 
boiler-feed pumps are in duplicate. It is a good investment to 
put a water meter in the feed line, and one capable of measuring 
hot water should be used. The meter should have a by-pass and 
be located at the pressure side of the pump, as shown. From the 
feed pumps the water is forced through the primary heaters and 
then through the auxiliary heater to the boilers. If the hot well 
is not provided with sponges or some material arranged to filter 
the oil from the air-pump discharge, a cloth filter should be placed 
between the feed pumps and the boilers. Each heater should 
have a by-pass, and in the pipe leading to each heater two valves 
should be placed, one used as a stop valve and the- other as a regu- 
lating valve, which should be adjusted when the plant is started, 
so that approximately equal amounts of water will pass through 
the heaters. It involves a little more complication to do this, 
but it insures each heater doing its full work. 

The arrangement shown in Fig. 31 provides for the use of a 
heater of the closed type between the engine and condenser, for 
of course an open heater could not be used in such a situation. 
It is not often the custom to place a heater between the engine 
and condenser, and where that is not done an open heater might 
be used to receive the exhaust steam of the auxiliaries, and if so, 
the arrangement of the feed-water piping would have to be dif- 
ferent from that shown. If the plant shown diagrammatically in 
Fig. 31 was provided with jet condensers the boiler-feed pumps 
might be arranged to draw their supply from the air-pump dis- 
charge, as well as from the source of the fresh-water supply and 
pump it through the heaters to the boilers. If ample feed water 
at low cost was available the air-pump discharge would probably 
be allowed to go to waste because of the grease in it and the 
pumps connected to draw fresh water. If the latter was under 



STEAM POWER PLANTS 



119 



pressure the water could be passed to an open heater first and the 
pump arranged to draw the water from it. This arrangement 
combined with an economizer is shown diagrammatically in 
Fig. 32. If a surface condenser was used the air-pump discharge 



Boilers. 



ISuOl 



1 r*-i\. 



O-O 



O-O 



•3: 



(Check Valvz. 
if Globe Valve, 



Injector Main, 



T. . (' 



Injector. 



[ Feed\ \Pumps\ 



gfc? 



Open Heahr 

&C\i 



By'Pass.' 



I Cold Wafer Suppfy 



T**i 



By^Pa 



All High Pressure Drips. 
By - Pass. Returns from Heating Sysfem Etc. 
enter Heater. 



Pass. 



Fig. 32. Feed Piping with Open Heaters. 

might be led to an open hot well, arranged to filter the water by 
means of sponges or excelsior, etc., located at a higher elevation 
than the heater so the water would flow to the heater by gravity 
and from the heater to the feed pumps at a lower elevation than 
the heater so that the pump suction would be under pressure. If 
the filter was of the closed type containing cloth or similar 
material it would have to be placed between the pumps and the 
boilers. High-pressure drips could be trapped into the heater, 
returns from the heating system could be connected with it, and 
fresh cold water could be added to the heater by a float valve 
when the demand of the pumps was in excess of the water enter- 
ing the heater from the condensers, heating system, drips, etc. 
The boiler-feed pumps would have to pump hot water with this 
arrangement, hence they should be constructed to do this. The 
pumps could deliver water to the boilers direct or first through 
an economizer where the water would be heated further by the 
waste gases from the boiler. An economizer is placed between 
the pumps and the boilers. Arrangements should be made to 
by-pass all heaters, economizers, meters, etc. 

If a live-steam purifier is used, which is a heater in which the 
feed water is exposed to the action of steam at full boiler pres- 
sure to precipitate scale forming salts in the purifier instead of 
having them precipitated in the boiler, the purifier is elevated 
above the boilers and receives the feed water after it has passed 
through all other heaters; and it is connected so that water will 
flow from it to the boilers by gravity. 



120 



STEAM POWER PLANTS 



In Fig. 31 one end of the feed-water main in the boiler room 
is provided with an injector connected to the fresh-water supply. 
It would be a better arrangement, perhaps, to have an independ- 
ent main from the injector, the main connecting with the feed 
pipe to each boiler through stop valves so that water from the 
injector or the feed pump could be supplied to any boiler in- 
dependent of the others, as shown in Fig. 33. 



"■ J — S. ,1 — L J * 




Fig. 33. Pipe Bracket designed by Sheaff & Jaasted. 



The method of running feed mains in a boiler room varies. 
Horizontal tubular boilers are frequently set with a number of 
boilers in one battery. Sometimes, therefore, the feed main is 
run along the fronts of the boilers just above the fire doors. 
Water-tube boilers are generally set two in a battery, so that if 
a pipe extends across the front it blocks the passageway between 
the batteries. With this type of boiler the feed main is sometimes 
run in a basement below the boiler room. Again, the mains are 
run on top of the setting. In the latter event a branch from 
the main should extend to the boiler front, at an elevation low 
enough so that the regulating valve, which should be of the globe 
type, may easily be reached by the boiler attendant. A pref- 




Plan of Engine Mouse. Cross-Section of Boilei- Mo 

Plate 13. — Power House, Southern Terminal Station, Boston, Mass. 

GEO. P. FRANCIS, CH. ENG'R; WESTINGHOUSE, CHURCH, KERR & CO., ENG'rS AND CONT'rS. 



STEAM POWER PLANTS 121 

erable arrangement is to keep the feed piping well overhead and 
provide an extension to the feed-valve spindle extending down to 
a convenient height above the floor. A check valve should be 
placed in the pipe, as shown. 

Feed-water piping for noncondensing plants with the closed 
type of feed-water heater is shown in diagram in Fig. 28. It 
is supposed that exhaust steam is used for heating and that the 
condensation is returned to the boilers. This may be brought 
back to one of the boiler-feed pumps, which can be connected 
to a return tank receiving the condensation in the heating sys- 
tem. The pump draws water from the tank and forces it through 
the feed-water heater to the boiler. A fresh-water pipe is led to 
the return tank and the supply is controlled by a float valve. If 
a feed-water heater of the open type is used, the condensation 
from a heating system is carried back to the heater, and usually 
enters it at the side or bottom and thus does away with the auto- 
matic pump and receiver. The boiler-feed pump draws its sup- 
ply from the heater and forces the water to the boilers. Fresh 
water under pressure, controlled by a float valve or ball cock in 
the heater, is supplied to the heater at the top, and it falls to the 
bottom in direct contact with the exhaust steam and is thus 
heated. Cold water is only supplied when the boiler-feed pump 
draws the water from the heater so fast that the water surface 
falls below a certain level. 

In electric stations it is frequently the practice, for safety's 
sake, to use a duplicate feed main from the pump to the boilers. 
With such an arrangement it is possible to test a boiler or group 
of boilers. If the steam piping is arranged so that one or more 
boilers can supply any one engine independently of the others, 
the duplicate boiler-feed main is of considerable value, for with 
such a duplicate system the steam used by an engine can be 
measured at any time and the condition of the engine determined. 
Boiler-feed pumps should always be in duplicate. 

Blow-off Piping. — Blow-off piping is subjected to sudden 
changes of temperature and stress and special care should be 
taken to guard against excessive expansion strains. It should 
be put together with extra heavy cast-iron fittings except on 
the blow-off from horizontal return tubular boilers, and in this 
case when the blow-off is connected to the bottom of the boiler at 
the rear, with an elbow in the pipe exposed to the fire, this fitting 



122 STEAM POWER PLANTS 

should be of malleable iron. Fittings and valves outside of the 
boiler setting should be flanged. Each boiler blow-off should 
have two valves or a blow-off valve with a plug cock inside of 
the valve. Many water-tube boilers are provided by the makers 
with an angle type of blow-off valve, and when this is used the 
cock can be placed between it and the boiler. Single blow-off 
valves are very apt to leak, due apparently to the cutting of the 
valve seat and disk by the scale blown from the boiler. With 
two valves this trouble is largely overcome. 

In buildings in cities where an ordinance prevents the blowing 
of boilers into the sewer the blow-off is frequently led to a tank 
vented to the atmosphere, the tank being provided with a coil 
of pipe through which cold water used for the boiler feed or for 
the hot-water supply of the building is circulated, for the purpose 
of cooling the water blown from the boilers before it is run into 
the sewer. Sometimes a cold-water connection is run to this 
tank and cold water is used for cooling. As the water blown 
from the boilers is frequently at a temperature way above the 
temperature at which water under atmospheric pressure evapo- 
rates, a certain part of the water blown from boiler will evaporate 
into steam, and means should be provided for disposing of this 
steam without injury. 

For large power plants the blow-off can be run into a specially 
constructed reservoir or cesspool roofed over and vented to the 
atmosphere. The blow-off main from the boilers can be con- 
nected at the top, and the discharge for the water can be through 
an overflow pipe extending from a point near the bottom of the 
cesspool to a point near the top then running horizontally to a 
sewer or to waste. With this arrangement the cooler water will 
be at the bottom and be drawn off first. 



CHAPTER VIII. 

MATERIALS FOR PIPING, PIPE SIZES, SEPARATORS, 
AND OILING SYSTEMS. 



Kind of Pipe. — " Standard " sizes of pipe of steel or wrought 
iron are usually used for steam piping. Table 20 contains the 
various dimensions of pipe, those up to and including 10-inch 

TABLE 20. —DIMENSIONS OF STANDARD-WEIGHT PIPE. 





a 






35 




a 

'3 . 




- Mo ® 

a> (Bo b 

3 ^*^ 02 


te, 
per 
150 
sure. 




s 




8 


u, 3 




c o 




•s? c s 


3 "£ "> 

a © _, © 


<D 
© 

s 


© 

°co 




CD 

2 


0) o 

© ° 
"3.8 


d 


o o 


o 
o 


Cg 


Bill 


a 


3 


00 


'ce 




© 




© 


© >, - bjO 


© >> .. M 




Q 


Dja 


C 


O CD © 


In 


O CD 


Q. 


hp-tj a> m 


W)+» a> co 




"«3 fc 




"3 5s 


r. " W 


C3 
© 


3§ 




iHl 


-Q.2 c 5 


3 

°GO 


a *> 
c © 


o 


3 0) 


S CO CO 


3 


G C 


W) 

'© 


1 "2 1 


■S>8R 


a 

H- 1 


<4 


H 


<j 


^ 


a 


^ 


£ 


Q 


Q 


Ins. 


Ins. 


Ins. 


Ins. 


Feet. 


Ins. 


Feet. 


Lbs. 


Lbs. 


Lbs. 


1 

ii 

n 

2 

2| 

3 


1.315 
1.66 
1.90 
2.375 

2.875 
3.50 


0.134 
0.140 
0.145 
0.154 
0.204 
0.217 


1.048 
1.380 
1.611 
2.067 
2.468 
3.067 


2.903 

2.301 

2.01 

1.611 

1.328 

1.091 


0.8627 
1.496 
2.038 
3.355 

4.783 
7.388 


166.9 

96.25 
70.65 
42.36 
30.11 
19.49 


1.670 

2.258 
2.694 
3.600 
5.773 
7.547 






















80 


113 


31 


4.00 


0.226 


3 . 548 


0.955 


9.887 


14.56 


9.055 


107 


151 


4 


4.50 


0.237 


4.026 


0.849 


12.730 


11.31 


10.66 


138 


194 


4i 

^2 


5.00 


0.247 


4.508 


0.765 


15.939 


9.03 


12.34 


173 


243 


5 


5.563 


0.259 


5.045 


0.629 


19.990 


7.20 


14.50 


218 


305 


6 


6.625 


0.280 


6.065 


0.577 


28.889 


4.98 


18.767 


315 


442 


7 


7.625 


0.301 


7.023 


0.595 


38.737 


3.72 


23.27 


422 


592 


8 


8.625 


0.322 


7.982 


0.444 


50.039 


2.88 


28.177 


545 


764 


9 


9.625 


0.344 


9.001 


0.394 


63.633 


2.26 


33.70 


694 


974 


10 


10.75 


0.366 


10.019 


0.355 


78.838 


1.80 


40.06 


872 


1223 


11 


12.00 


0.375 


11.25 


0.318 


98.942 


1.455 


45.95 


1079 


1514 


12 


12.75 


0.375 


12.000 


0.293 


116.535 


1.235 


48.98 


1275 


1788 


13 


14.00 


0.375 


13.25 


0.273 


134.582 


1.069 


53.92 


1468 


2060 


14 


15.00 


0.375 


14.25 


0.254 


155.968 


.923 


57.89 


1702 


2385 




16.00 


0.375 


15.25 


0.238 


177.867 


.809 


61.77 


1940 


2722 




18.00 


0.375 


17.25 


0.212 


225.907 


.638 


69.66 


2462 


3452 




20.00 


0.375 


19.25 


0.191 


279.720 


.515 


77.57 


3050 


4275 




22.00 


0.375 


21.25 


0.174 


354.66 


.406 


85.47 


3870 


5425 



pipe being the Briggs standard. The other sizes are in common 
use. As ordinary merchant pipe may vary in thickness from 

123 



124 STEAM POWER PLANTS 

the standard, " full-weight " pipe should be asked for. Full- 
weight pipe may vary 5 per cent from the standard thickness. 
In the connection between a boiler and a steam main, or the 
main and the engines, long bends made of pipe are an advantage, 
for several reasons'. First, they reduce the friction very much; 
second, their use reduces the number of joints likely to leak; 
third, such a connection is very much more flexible than one 
composed of two straight pieces of pipe connected by an elbow. 
Their greater flexibility is of great advantage in taking care of 
expansion after the piping is in place, and, furthermore, they are 
much easier to connect when erecting the piping. No matter 
how much care is taken in facing the flanges off square, it almost 
always happens that the flanges of the boiler nozzles are not in 
perfect alignment, or exactly horizontal, so that a considerable 
strain is introduced in the piping in forcing the abutting flanges 
to a seat. It is much better to make the bends in the piping of 
steel or wrought iron than copper, although the latter has been 
used to some extent. At the temperature the copper is subjected 
to in brazing the joint, the fibrous nature that copper acquires in 
rolling is destroyed and a serious reduction of its tensile strength 
and ductility results. Mr. James B. Berryman of the Crane 
Company states that unless the bends are of very short radius 
they are generally made of standard pipe for pressures of 125 
pounds or less, full-weight pipe up to 175 pounds, and extra- 
heavy pipe for higher pressures. 

Size of Steam Pipes. — It has been the custom to so proportion 
steam-supply pipes for engines that the maximum velocity of 
steam flowing through them will be about 6000 feet per minute. 
The pipe size can be obtained by assuming that the area of the 
steam pipe in square inches multiplied into the maximum ve- 
locity of steam in feet per minute is equal to the piston area in 
square inches multiplied into the piston speed in feet per minute. 
■If the cut-off is at one-third stroke the average velocity of steam 
would then be about 2000 feet per minute. 

Friction would cause a considerable drop in pressure, with 
small sizes of pipe, when proportioned by this rule. Some ex- 
periments upon the flow of steam in pipes in a paper in Volume 
XX, Transactions of The American Society of Mechanical Engi- 
neers, by Professor R. C. Carpenter, give some data that is of 
value. The tests were made upon 1-, 1 J-, 2- and 3-inch pipes with 



STEAM POWER PLANTS 



125 



lengths varying from 90 to 250 feet. The formula derived from 
the experiments checks very closely with the results obtained 




Fig. 34. Pipe Bracket. 

by M. Ledoux, who experimented with pipes varying from 1.85 
inchc3 to 3.94 inches in diameter and with lengths varying from 
328 feet to 1082 feet. 

Professor Carpenter uses the formula 

1 



P = 



20.663 



/ 3.6\F»L 

n 1 + Tfe' 



in which P equals the loss of pressure in pounds per square inch, 
d the diameter of the pipe in inches, W the flow of steam in pounds 
per minute, w the flow in pounds per second, D the density or 
weight per cubic foot, L the length of pipe in feet and K a con- 
stant taken, as a result of the experiment, at .0027. Table 21, 
which was calculated by Mr. E. C. Sickles, is based upon the 
formula and was deduced by making every factor constant ex- 
cept the diameter, length of pipe, and discharge. The left-hand 
vertical column of the table contains the diameters (d) of the 
pipes, and the top horizontal column the length (L) in feet, while 
the body of the table gives values of (W) the pounds discharged 
per minute. Professor Carpenter explains the table as follows: 
" Thus, for instance, a 10-inch pipe 250 feet long will deliver 
712 pounds of steam per minute with a drop of one pound in 
pressure, if there exists an average absolute pressure of 100 



126 



STEAM POWER PLANTS 



pounds; or, if all other conditions hold except the length of 
pipe, which varies, it may be seen that for 100 feet the discharge 




Fig. 35. Pipe Support designed by Dean & Main. 



is 1126 pounds, for 400 feet 563 pounds, and so on for any number 
of feet given in the table. 

" If any intermediate length of pipe is used other than those 
given in the table, the discharges given by the table may be 
corrected by consideration of the fact that the weight of dis- 
charge is inversely proportional to the square root of the length 
of the pipe. 

" To meet the conditions where other average absolute pres- 
sures than 100 pounds exist, and higher drops than one pound are 
assumed, it is only necessary to use suitable factors which are 
calculated by means of the fundamental formula, and graphically 
represented by Curves 1 and 2, Fig. 36. 

" As an illustration of the use of the tables and curves, suppose 
it is desired to find what size pipe will be required to deliver 
1000 pounds of steam per minute a distance of 1000 feet, the 
initial pressure of the steam being 157.5 pounds, and the final 
152.5 pounds by gauge. Solution — It will be best to reduce all 
conditions to those of the tables and find the discharge, and from 
this the size of the required pipe. Looking at Curve 2, we find 
the factor of discharge for a 5-pound drop is about 2.23 times 
that for a 1-pound drop. Therefore, dividing the required dis- 
charge of 1000 pounds by 2.23, we have about 450 pounds dis- 
charge for a 1-pound drop. 

" Again, the average pressure is 155 + 15, or 170 pounds abso- 
lute, and from Curve 1 it may be found the factor of discharge is 



STEAM POWER PLANTS 



127 



TABLE 21. — FLOW OF STEAM IN PIPES. DELIVERY IN 
POUNDS PER MINUTE BY PIPES OF GIVEN DIAMETERS 
AND LENGTHS. (ABSOLUTE PRESSURE 100 POUNDS — 
DROP IN PRESSURE ONE POUND.) 



Diam- 


Length in feet. 


eter in 






















inches. 


50 


100 


150 


200 


250 


300 


350 


400 


500 


600 


3 

i 


1.55 


1.10 


.898 


.700 


.698 


.633 


.589 


.550 


.491 


.450 


1 


3.10 


2.20 


1.79 


1.55 


1.39 


1.26 


1.17 


1.10 


.982 


.900 


li 


6.90 


4.88 


3.93 


3.44 


3.08 


2.81 


2.62 


2.44 


2.18 


1.96 


■li 


9.29 


6.52 


5.83 


4.62 


4.14 


3.77 


3.50 


3.26 


2.91 


2.67 


2 


21.6 


15.2 


12.50 


10.8 


9.82 


8.82 


8.37 


7.63 


6.81 


6.23 


2| 


35.9 


25.4 


20.8 


17.9 


16.2 


14.62 


13.6 


12.7 


11.3 


10.4 


Diam- 


Length in feet. 


eter in 






















inches. 


100 


250 


400 


550 


700 


850 


1000 


1300 


1600 


1750 


3 


46.0 


29.2 


23.0 


19.6 


17.4 


15.8 


14.5 


12.7 


ll.fi 


11.0 


3* 


69.5 


44.6 


34.7 


29.6 


26.3 


23.8 


22.0 


19.2 


17.4 


16.6 


4 


97.6 


61.8 


48.8 


41.5 


36.7 


33.5 


30.8 


27.1 


24.4 


23.3 


4- 1 

^2 


132.9 


84.1 


66.4, f 


5 56.6 


50.1 


45.6 


42.0 


36.75 


33.2 


31.8 


5 


180.7 


114.3 


90.3 


76.9 


68.2 


62.1 


57.1 


50.0 


45.2 


43.2 


6 


296.5 


187.4 


148.2 


125.8 


111.8 


101.8 


93.7 


82.2 


74.1 


71.0 


7 


437 


276 


218 ■ 


186 


165 


150 


138 


121 


109 


104 


8 


625 


394 


312 


266 


236 


214 


197 


173 


156 


149 


9 


853 


589 


426 


363 


322 


292 


269 


236 


213 


204 


10 


1126 


712 


563 


480 


425 


386 


356 


312 


281 


269 


11 


1447 


915 


723 


617 


546 


496 


457 


401 


361 


346 


12 


1887 


1192 


943 


803 


714 


648 


598 . 


523 


472 


451 


13 


2238 


1415 


1119 


954 


846 


767 


707 


620 


559 


535 


Diam- 




Length in feet. 




eter in 






















inches. 


100 


200 


300 


500 


800 


1000 


1400 


1800 


2000 


2200 


14 


2,714 


1920 


1567 


1213 


959 


858 


725 


639 


606 


578 


15 


3,250 


2300 


1873 


1453 


1149 


1028 


868 


766 


726 


693 


16 


4,000 


2830 


2315 


1785 


1413 


1268 


1072 


945 


895 


854 


17 


4,500 


3210 


2635 


2021 


1591 


1424 


1200 


1061 


1006 


962 


18 


5,211 


3685 


3008 


2330 


1843 


1648 


1393 


1228 


1165 


1111 


19 


5,992 


4237 


3459 


2680 


2119 


1895 


1602 


1412 


1340 


1278 


20 


6,839 


4835 


3948 


3059 


2418 


2163 


1828 


1612 


1529 


1458 


22 


8,743 


6183 


5048 


3910 


3093 


2765 


2337 2061 


1955 


1864 


24 


11,308 


7990 


6535 


5065 


3995 


3580 


3023 2665 


2535 


2415 



1.248 greater than for 100 pounds absolute. Therefore, dividing 
450 pounds by 1.284 we have 350 pounds on the basis of the con- 
ditions given in Table 21; and looking under 1000-feet lengths 



128 



STEAM POWER PLANTS 



1.540 
1.500 
1.460 
1420 
1.880 
1.340 
1.800 
1.260 
1.220 
1.180 
1.140 
1.100 
1.060 
1.020 
0.980 
0.940 
0.900 
0.860 























2\l 






















































































































































































































































































— 












































































































P 
























































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































































2\ 






















1, 
































































































































































































































































































































































































































































































/ 


V€ 


ra 


?e pte 


an 


[ p 


res 


su 


re 


in 


Po 


in 


Is 


Ab 


sol 


ut< 
















80 


9 





1 


30 


1] 





120 


1! 





h 


to 


1! 


50 


160 


1 


"0 


V 


10 


1'. 





2 


X) 


2 


10 


2; 


>0\230 
















| 














1 
























u 



4.40 
4.20 



4.00 . 
c» 
9 

3.80 £ 

o 

3 



3.20 u 

d 

3.00 w 
A 
o 



at 
O 

2.60 -a 

t 

2.40 § 



2.20 



2.00 



1.80 



1.60 



1.40 



1.20 



22 21 20 19 18 37 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 10 
Pounds— Drop In Pressure 



1.00 



Fig. 36. 

for the discharge nearest to 350 pounds, we find a 10-inch pipe 
discharges 356 pounds per minute; therefore, it would be satis- 
factory. " 

Kind of Fittings. — There are two kinds of fittings used in 
steam piping, the screwed and the flanged fittings. The former, 
as the name implies, are put together with a screw thread, while 
the flanged fittings are bolted together. Screwed fittings are 
used to some extent in plants where the steam pressure is low, 80 
pounds or under, and sometimes with higher pressures. Adja- 
cent pieces of pipe may be coupled together by means of screw 
couplings or by means of companion flanges. Screw fittings 
have the advantage that once made up properly they are not 
likely to leak, while flanged fittings have to be put together with 
some kind of gasket which may blow out or require renewal. 



STEAM POWER PLANTS 



129 



Flanged connections between adjacent pieces of pipe and 
flanged fittings and valves possess the great advantage of being 
easily taken apart and repaired, and this is so great an advantage 
that flange construction is much preferred in high-grade work. 
In screw work it is customary to specify that occasional flanges 
are to be provided in piping to permit of its being taken down 
easily. The most used type of flange is shown in Fig. 37. The 
pipes are screwed into the flanges as shown. On July 18, 1894, 
committees of the American Society of Mechanical Engineers, of 
the National Association of Steam and Hot-water Fitters, and of 
manufacturers of fittings, met and adopted a schedule for the 
dimensions of flanges and this schedule is known as the A. S. M. E. 
or the Master Steam Fitters' flange schedule. This schedule 
is printed in Table 22 below. Flanges dimensioned in accord- 
ance with this schedule are considered strong enough for a steam 
pressure of 100 pounds. For higher pressures, a schedule shown 

TABLE 22. — SCHEDULE OF STANDARD FLANGES. 

Adopted July 18, 1894, by a committee of the Master Steam and Hot- 
water Fitters' Association, American Society of Mechanical Engineers 
and Valve Fitting Manufacturers. Suitable for pressures under 100 pounds 
per square inch. 



Size of 
flange, pipe 
size X diam- 
eter. 


Diameter 
of bolt 
circle. 


Num- 
ber of 
bolts. 


Size of 
bolts, pres- 
sure under 
80 pounds. 


Size of 
bolts, pres- 
sure 80 
pounds and 
over. 


Flange 
thickness 
at hub for 
iron pipe. 


Flange 
thickness 
at edge. 


Width 

of flange 

face. 


2X6 


4! 


4 


! x2 i 


1X2 




5 

8 


2 


2|X 7 


5J 


4 


2 X2j 


|X21 


1 1 

A 8 


11 

16 


21 


3 x X 7 I 


6 


4 


2Ai2 


8 X^2 


1 1 

x 4 


3 
4 


21 


3^ X 82 


7 


4 


2 X^2~ 


g X^2 


1 1 
A 4 


13 
16 


22- 


4X9 


7i 
• 2 


4 


|X2f 


|X2| 


1 3 
A 8 


15 

1H 


2| 


4iX 91 


7! 


8 


1X3 


1X3 


1 3 
•••8 


15 
16 


2| 


5 X10 


8| 


8 


1X3 


1X3 


1 1 
^2 


15 
16 


2h 


6 Xll 


9| 


8 


f X3 i 


|X3 


1 1 
±2 




2| 


7 xm 


iof 


8 


8aoj 


4X04 


-I 1 

x 2 


1 1 

x 16 


2! 


8 X13| 


Ill 


8 


8 X02 


|X3| 


1 3 


1 1 


n 


9 X15 


131 


12 


8 Xt>2 


4X02 


1 3 

L 4= 


1 1 
x 8 


3 


10 X16 


14| 


12 


!X3| 


8 XOfj 


2 


1 3 

x 1 6 


3 


12 X19 


17 


12 


|X3f 


1X3! 


2 


1 1 


3^ 


14 X21 


18| 


12 


|X41 


1 X41 


2 


1 3 
x 8 


3| 


15 X22| 


20 


16 


8 X4j 


1 X41 


2 


1 3 

L 6 


si- 


16 X23| 


211 


16 


1X41 


1 X41 


21 


1 7 
- 1 16 


si 


18 X25 


22| 


16 


1 X4| 


HX4f 




1 iC 


3| 


20 X27| 


25 ' 


20 


1 X5 


UX5 




1 1 1 
1 16 


3| 





130 



STEAM POWER PLANTS 



in Table 23 was adopted June 28, 1901, and this is suitable for 
pressures from 125 to 225 pounds per square inch. Flanged 
fittings, that is, elbows, ties, crosses, etc., are made by a number 
of manufacturers, and attention is drawn to the fact that the face- 
to-face and the face-to-axis dimensions vary with the different 
makes although the flange dimensions are standard. Specifica- 
tions for flanges should require that the holes be drilled in the 



TABLE 23. — SCHEDULE OF STANDARD FLANGES FOR EXTRA 
HEAVY STEEL PIPE. FITTINGS, AND VALVES. 



Adopted June 28, 1901, by valve and fitting manufacturers. 
for pressure from 125 to 250 pounds per square inch. 



Suitable 



Size of pipe, 
inches. 


Diameter of 
flange, 


Thickness of 
flange, 


Diameter of 
bolt circle, 


Number of 
bolts. 


Diameter of 
bolts, 


inches. 


inches. 


inches. 


inches. 


2 


6! 


7 
8 


5 


4 


5 

8 


91 

• ^2 


n 




51 


4 


3 
4 


3 


81 


1 1 
x 8 


6| 


8 


5 
8 


3! 


9 


1 3 

x 16 


n 


8 


5 

8 


4 


10 


■1 1 
A 4 


71 


8 


3 
4 


4-i 


10| 


1 5 


8! 


8 


3 

4 


5 


11 


1 3 
A 8 


n 


8 


3 
4 


6 


12! 


1 7 


10f 


12 


3 

4 


7 


14 


1 1 
L 2 


111 


12 


7 
8 


8 


15 


1 5 
L 8 


13 


12 


7 
8 


9 


16 


1 3 
A 4 


14 


12 


7 
8 


10 


m 


1 7 
x 8 


15| 


16 


7 
8 


12 


20 


2 


17! 


16 


7 
8 


14 


22| 


9i 

■^8 


20 


20 


7 
8 


15 


23| 


2t% 


21 


20 




16 


25 


2i 


22! 


20 




18 


27 


2| 


24! 


24 




20 


29| 


2! 


26f 


24 


1 1 
x 8 


22 


31! 


2| 


281 


28 


1 1 
^8 


24 


34 


2| 


3H 


28 


1 1 
*8 



flange to straddle a vertical plane passing through the axis of the 
pipe. In the best work, where the flange is screwed on the pipe, 
the pipe and flange are carefully threaded and the pipe screwed 
into the flange until it projects slightly beyond its face. The 
inner circumference of the flange at the face of the flange is then 
struck with a hammer, or peaned, as it is called. The pipe and 
flange are then put into a lathe where both are faced off. It is 
very essential that the pipe and flange be faced off in the lathe 
in order that the face of the flange will be perpendicular to the 



STEAM POWER PLANTS 



131 



axis of the pipe. Another method of securing this result is to 
thread the flange on a mandrel so that the axis of the thread will 
be perpendicular to the face of the flange. Pipe over 18 inches 
in size cannot be threaded so the flanges are riveted on pipes over 
that size, or else shrunk on. In the latter case an accurately 
bored flange is heated and forced on the end of the pipe. Some- 
times rivets are used with smaller pipe than 18 inches but more 
often with larger sizes. Cast-iron flanges riveted to the pipe are 
apt to leak as it is very difficult to make a joint that will stay 
tight. 

The difficulty with the flange shown in Fig. 37 is the tendency 
to leak through the thread. This can be overcome by good 
workmanship, and some manufacturers have devoted a great deal 
of attention to making flanges of this type for high steam pres- 
sures. This type of flange is frequently put together with a 
copper gasket, either in the form of a flat or a corrugated ring. 
There are various patented packings that have also given excel- 
lent satisfaction. In the flange shown by Fig. 38, which was 





Fig. 37. 



Fig. 38. 



used some years ago with a good deal of success, there is a circular 
tongue and groove, as shown, the groove containing a ring of 
copper as a gasket. One objection to this flange is that in places 
where the piping is concentrated and the connections short, it is 
difficult to spring the flanges apart a sufficient amount to take 
out a section of pipe for repairs. 

The objection to any screwed flange is the tendency, unless the 
workmanship be of the best, for steam to leak through the joint 
between the flange and the pipe. A method of overcoming this 
leakage is shown in Fig. 39. The sketch from which the cut 
was made was furnished by Mr. George I. Rockwood, Mem. Am. 
Soc. M. E., who designed the flange. The pipe is of steel, and 



132 



STEAM POWER PLANTS 



the flange is slipped over it, and the end of the pipe heated and 
flanged, as shown. In the original design the abutting faces of 
the flange are cut away so as to calk the joint. The " Wal- 
manco " joint, made by the Walworth Manufacturing Company, 





Fig. 39. 



Fig. 40. 



has a recess in the flange in which the pipe is expanded as shown 
in Fig. 40. 

Cast-iron pipe with flanges cast on the ends, as shown in Fig. 
41, have been used by some engineers, but the material is so 
treacherous in nature that its use is to be deprecated except for 
feed mains Where the water is bad. 

Steel pipe with forged-steel flanges welded on the end of the 
pipe, shown in Fig. 42, has been used very successfully. The 




mr,iMuM»»»»»»»». 



I 



^mUMmuM»UM»«uuaa 



Fig. 41. 



Fig. 42. 



process of manufacture has been developed by the National Tube 
Company, which stated that in making the pipe a forged flange 
is bored out and forced on to the end of the pipe. It is then 
heated in a furnace and welded by means of a hammer. The 
flange is then faced and the bolt holes bored out. 

The type of flange designed by Mr. Rockwood has been mod- 
ified somewhat for pipe sizes 5 inches and over. The faces 



STEAM POWER PLANTS 133 

of the flanges are no longer cut away on the bevel shown and the 
flange that is slipped on the pipe should be of rolled steel. This 
type of joint is used for high-grade work more than any other. 
In the best work it is customary to specify that the flanged part 
of the pipe shall be faced in a lathe on the front and back, and 
that after facing it shall have a thickness equal to the original 
thickness of the pipe. For pipe under 5 inches in diameter the 
joint shown in Fig. 37 is used. 

Specifications for Piping. — When an engineer prepares accu- 
rate and complete scale drawings of the entire system of pipe 
fittings, etc., the written specifications can be quite brief. They 
should call for bids on the engineer's drawings, name the local- 
ity of the power house, give the time allowed to complete the 
work, and specify by name or make the following, if they are to 
be used, and are not marked on the drawings: Steam valves; 
water valves; reducing valves; back-pressure valves; steam traps; 
injectors; kind of packing used between the flanges; kind of pipe 
covering. The method of supporting pipes should be described, 
if it is not indicated in the drawings. The kind of fittings and 
pipe wanted should be clearly stated. The following extracts 
from a specification may be of interest: 

All pipes carrying steam under boiler pressure, all pipes carrying water 
under the pressure of the city mains, all pipes carrying water under boiler 
pressure, including the blow-off piping, are to have extra heavy valves, flanges, 
and fittings good for 250 pounds steam pressure. In all of the piping 5 inches 
in diameter and over the Rockwood type of joint (sometimes called the Van 
Stone joint) with rolled steel flanges shall be used. The joint shall be made 
by slipping the rolled steel flange over the end of the pipe which shall be 
heated and flanged, after which the flanged part of the pipe shall be faced off 
in a lathe on the front, back, and on the outer rim, and after being so faced 
the flange shall be equal in thickness throughout to the original thickness of 
the pipe. In the above-mentioned piping all flanges in pipes 5 inches in size 
and under shall be extra heavy cast-iron flanges screwed on the pipe, flanges 
to be faced on a manhole after threading, or the flange shall be refaced in a 
lathe after it is screwed on to the end of the pipe. 

All piping except that mentioned in the preceding paragraph to have 
standard-weight fittings, flanges, and valves except where couplings are per- 
mitted as hereinafter specified. 

All pipes 2 inches in diameter and over carrying high-pressure steam or 
water under boiler pressure or under the pressure of the city mains, and all 
other pipes 3 inches in diameter and over shall have flanged fittings, and all 
other fittings shall be screwed fittings. 

All pipes 2 inches in diameter and over carrying high-pressure steam. or 



134 STEAM POWER PLANTS 

water under boiler pressure and all other pipes 3 inches in diameter and over 
to be connected together by means of flange unions; other pipes may be joined 
together by standard wrought-iron couplings. 

For extra heavy flanges, fittings, and valves the flange dimensions and 
drilling shall correspond with the 1901 Master Steam Fitters' schedule for 
steam pressures of from 125 to 250 pounds. 

For standard-weight flanges, valves, and fittings the flange dimensions and 
drilling shall correspond to the Master Steam Fitters' schedule of 1894 for 
steam pressures up to 100 pounds. 

All pipes 1^ inches in diameter and over to have final connections to a 
trap, tank, heater, or any other apparatus made by means of flange unions. 
For pipes smaller than 1| inches final connections shall be made with heavy 
bronze unions. 

All fittings in boiler-feed lines shall be extra heavy cast iron (or of cast 
brass made from the same pattern as extra heavy cast-iron fittings). 

All flanges in high-pressure lines shall be put together with thin corrugated 
copper gaskets, and all flanges in low-pressure lines shall be put together with 
approved rubber gaskets. 

Except when extra heavy steel pipe or brass pipe is specified all pipe must 
be full-weight steel pipe equal to the Briggs standard up to and including 
10 inches, and to the Morris Tasker standard over 10 inches. Pipes carrying 
cold water to be galvanized. 

All threads on pipes to be full and clean-cut and no other lubricant than 
oil and graphite shall be used in screwing up pipe. Calking of threads will 
not be permitted. 

The boiler-feed line from the pumps to and around the heater to the boilers 
including the branches to be brass, iron-pipe size. 

Valves. — It has been the practice for many years in stationary 
plants, particularly large ones, to use gate valves in high-pressure 
steam. lines, while the so-called globe valve seems to have had the 
preference in marine work. The author's experience with gate 
valves for steam pressures of from 100 to 150 pounds has not 
been as satisfactory as with globe valves on account of an appar- 
ent greater tendency of the gate type to leakage. One objection 
to the use of globe valves in steam lines lies in the fact that they 
introduce a pocket where water might collect. By placing the 
valve with the stem in a horizontal position this is largely over- 
come, and in large valves the bodies may be dripped when neces- 
sary. It is believed that globe or angle valves might be used 
for sizes, 10 inches in size and under for all high-pressure steam 
lines, and some of these valves with extra heavy iron or steel 
body with special seats and disks will give excellent satisfaction. 
Gate valves are usually used on exhaust and low-pressure steam 
lines and in all water lines excepting regulating or feed valves 



STEAM POWER PLANTS 135 

on boilers which should be of the globe type. Gate valves sub- 
jected to high pressure, 8 inches in diameter and over, should 
be provided with by-passes; when over 4 inches in size they 
should have rising spindles. All valves should be capable of 
being packed while under pressure. Two-inch valves and under 
usually have brass or special composition bodies with cast-iron 
bodies when over 2 inches in size. Some of the better valves 
for very high pressures have bodies of cast steel. There are 
few things about a power house that will cause so much trouble 
and annoyance as poor valves and the greatest care should be 
taken to make a proper selection. 

Pipe Hangers. — Pipes should be supported in from 10- to 
18-foot intervals; the smaller the pipes the more frequently they 
should be supported. The greatest care should be taken to 
hang or support pipes so they may expand freely. Bracing is 
necessary in some situations to stop vibration. Pipe hangers 
should be made of wrought iron or steel. 

Covering Pipes. — Steam pipes should be covered for the 
double purpose of saving the latent heat in the steam that would 
otherwise be lost, to prevent steam-using machinery from being 
damaged by water of condensation, and in some instances, nota- 
bly in buildings, for reducing the temperature of rooms iu 
which power plants are located. With coal at $3 per ton, 10 
feet of uncovered 6-inch pipe will cause an annual loss under 
average conditions of over $5 per year. A good covering that 
would reduce his loss to $1 per year will only cost about $5. 
From this it will be seen that it pays under most conditions to 
buy the best covering obtainable, and in making a selection the 
question of durability should be looked into fully as much as 
the efficiency of covering when new. Cheaper covering may be 
used on heating and low-pressure lines when the greater heat 
transmitted by the cheaper covering will not cause a loss. In 
underground power plants, where artificial ventilation is neces- 
sary to reduce the temperatures to an endurable degree, the best 
covering for all hot pipes is worth its cost. 

Some extracts from a specification for pipe covering follow. 

All hot pipes furnished under this contract, also the branch feed pipes on 
the boilers as far as the stop valves, shall be covered with magnesia sectional 
covering of one or more thicknesses as specified. Drip pipes in trenches are 
not to be covered. All sectional covering shall be neatly banded with black 
iron bands. 



136 STEAM POWER PLANTS 

All high-pressure steam lines shall have a double nonconducting covering 

equal to double the standard thickness as given in the catalogues of the 

Co., or the Co., and all covering shall be furnished and applied by one 

of the firms mentioned, or by any other manufacturer satisfactory to the 
engineer. Where double thicknesses of covering are applied they shall be laid 
so as to break joints as far as possible. 

All fittings and valves excepting valve bonnets shall be covered with block 
magnesia of the same thickness as covering on adjacent pipes and finished in 
a hard plaster. The flanges shall be covered with plastic magnesia 1 inch 
thick and finished in a hard plaster. 

All sectional covering shall be round and smooth and all ends butt evenly 
and tightly together. No damaged or broken sections shall be used. When 
covering is formed from blocks care shall be taken to see that the blocks are 
properly applied and securely wired, with joints closed with plastic magnesia. 

The steam separators, the reheaters on the compound engine, and all steam 
piping furnished by the engine builder, the grease separator, feed-water heater, 
the return drip and blow-off tanks, and the heads of the boiler drums shall 
be covered with 2-inch magnesia blocks wired on and then finished in a hard 
plaster. 

All nonconducting material on exposed pipes shall be covered with resin- 
sized paper over which there shall be an outer covering of 10-ounce canvas 
sewed on and painted. All block or plastic covering shall be covered with 
8-ounce canvas neatly cut and fitted, pasted on and painted. 

Contractor shall cover the steam cylinders and valve chests of all pumps 
with magnesia blocks 2 inches thick, put on so as to be easily removable. 

All so-called magnesia- covering shall contain not less than 85 per cent 
carbonate of magnesia. 

Paint all nonconducting material exposed to view with two coats of cold- 
water paint, excepting within five feet of the floor, where two coats of lead- 
and-oil paint of color selected by the engineer shall be used. 

Cheaper forms of covering than 85 per cent carbonate of magnesia are the 
so-called air-cell coverings made by several manufacturers, in which one layer 
of asbestos paper fluted to form the air cells is wrapped over another layer 
until a sufficient thickness is obtained. When it is desired to economize this 
or other cheaper coverings may be used on low-pressure work, and the outer 
canvas jacketing and painting may be omitted and all plastic or block magnesia 
may be finished in a hard plaster. 

Grease Separator. — In noncondensing plants where the ex- 
haust steam is used for heating or any manufacturing purpose 
a grease separator should be used. This may; be the small 
separator, usually of cast iron, which forms a slight enlargement 
in the exhaust pipe, with various forms of baffle plates that are 
intended to separate the grease and allow it to flow into a cham- 
ber in the bottom of the separator, from which it is drawn off by a 
trap. A more efficient type is that in which a large steel tank, 
about 4 feet in diameter and 8 feet long for a 14-inch main, is 




Plate 14. — Cross Section, Manhattan Railway Company's Power Station, New York City. 

GEORGE H. PEGRAM, CH. ENG'r; W. E. BAKER, MECH. ENG'R; L. B. STILLWELL, ELEC. ENG'R. 



STEAM POWER PLANTS 



137 



. Scale. 
O' 4' 8' I2 / 16' 

I 1 1 1 I ! i ■ i 



II 






[=■■= 


;-Js .■-■■■>,■.-.■;■ 


oo 

'■■!&:-:-V.?l.-!tU>lfc.-:-A- -.\: :/*..■■.■>.■*•■*;■ 


OO 


' — < 


IT" 




ELEVATION OF BOILER PIPING. 



DETAIL OF PIPE SUPPORT. 




METHOD OF CONNECTING DUPLICATE MAINS TO BODLER8. 

Fig. 43. Steam-piping Details at Great Northern Paper Co. (Sheaff and 

Jaasted, Engineers.) 



138 STEAM POWER PLANTS 

used, the tank being placed horizontally. The steam enters the 
top at one end and passes out at the other end of the tank, also 
at the top. Various forms of baffles to catch the grease are > 
placed within the tank. The large sectional area of the separator 
gives the particles of grease and condensed steam a chance to fall 
to the bottom and collect there, from which they are drawn off 
by a trap. Separators of this type, and there are several on the 
market, are highly efficient, and if properly proportioned and used 
will remove practically all of the oil from exhaust steam, so that 
the condensation may be safely returned to the boilers. This 
separator, however, will not remove the oil sufficiently to over- 
come a cloudy appearance to the condensation of exhaust steam, 
due apparently to the fact that a certain part of the oil is volatil- 
ized and passes through the system in volatile form to be con- 
densed on such cooling surfaces as it may come in contact with. 

Steam Separators. — Steam separators are placed in steam 
pipes for the purpose of removing any condensation that may 
form or find its way into the pipe. They are made either in the 
form of a casting or a receptacle made of sheet steel with suitable 
inlet and outlet nozzles, and of sufficient volume to allow the 
steam to be so reduced in velocity as to permit the water to 
collect in the separator from which it may be drawn off by a trap. 
The receiver separator is usually placed close to a steam-engine 
cylinder, sometimes on top of the throttle valve, and its volume 
is so large as to furnish a reservoir of steam at the engine and do 
away with the intermittent flow of steam that occurs in the steam 
pipe, due to the opening and closing of the engine valves. This 
intermittent flow of steam has proved to be very objectionable 
in power plants in buildings, by causing vibration which has been 
overcome by the installation of a large receiver separator of this 
type. They are usually made with a volume two or three times 
the volume of the engine cylinder. Separators are absolutely 
necessary for steam engines with a positive stroke when there is 
any chance of water being present in the steam, to prevent the 
engine from being wrecked. 

Steam Traps. — There are many kinds and makes of steam 
traps on the market, and while many have given excellent satis- 
faction one should consider that it is only a question of time when 
a trap will begin to leak and be a source of expense. Traps are 
of the pot, float, or expansion type. The pot traps are those 



STEAM POWER PLANTS 139 

having a pot in the interior that when filled by the entering con- 
densation operates the valve, allowing it to discharge in an inter- 
mittent manner. Float traps, as the name implies, contain a 
float inside of a receiving chamber controlling the discharge valve, 
opening when the condensation in the trap reaches a certain level. 
Expansion traps contain some expanding device that closes the 
discharge valve when exposed to the higher temperature of 
steam and opens when in contact with cooler water of condensa- 
tion. In selecting traps care should be taken to see that parts 
likely to wear, such as valves and seats, may be renewed easily 
and replaced at slight expense. Traps should be connected to 
piping by means of brass unions or flanges so they may be easily 
disconnected for repairs, and they should be provided with a 
by-pass with the necessary valves, usually three, so the trap 
may be used or not as desired. Globe valves should be used in 
trap connections. Traps will not discharge naturally against a 
greater pressure than the pressure of steam entering them, a fact 
that is sometimes overlooked in steam-plant design. 

Engine -oiling Systems. — There are two systems usually used 
for supplying oil to engines ; one in which sight feed oil cups are 
placed on the various bearings, and the combination of these cups 
and a central oiling system where oil is pumped into elevated 
tanks and is thence conveyed by gravity through a system of 
pipes to the bearings, from which it is collected and run also 
by gravity to an oil filter located at some lower level than the 
engines. The filtered oil is again pumped to the overhead tank 
and is thus used over and over again, thereby effecting a con- 
siderable saving in the amount of oil used. Oil feeds used in this 
system are usually fed either from the central oiling system 
or from the cup itself which may be filled by hand. With the 
central oiling system a much more liberal supply of oil may be 
supplied to a bearing, thus producing better lubrication and to 
some extent less frictional loss. Cylinder lubrication may be 
obtained from the sight feed gravity oiler in which the pressure 
of water in a vertical pipe about 3 feet long, extending from the 
steam pipe to the lubricators, is utilized to force the oil into the 
steam-supply pipe. A much better device is the more modern 
force-fed lubricator which consists of an oil reservoir fitted with 
a pump attached to some moving part of the engine so as to 
supply a definite quantity of oil with each stroke of the engine. 



140 STEAM POWER PLANTS 

These pumps are particularly valuable in lubricating pumps 
when the speed is variable. 

A specification for an oiling system for an office building plant 
is given in the chapter on " Engine Specifications " in the specifi- 
cations for a Corliss engine. 



CHAPTER IX. 
CONDENSERS AND PUMPS. 

The purpose of attaching a condenser to a steam engine is to 
remove part of the pressure of the atmosphere, by creating a par- 
tial vacuum, from one side of the piston, and thus increasing the 
effective pressure acting upon the other side. If an engine is 
running without a condenser, with a mean effective pressure of 
40 pounds, and a condenser is added removing 12 pounds from 
the back pressure caused by the pressure of the atmosphere, the 
mean effective pressure would be increased, theoretically, to 52 
pounds, and the power would be correspondingly increased. If, 
however, the work done remains the same, the increased mean 
effective pressure, 52 pounds, can be reduced to 40 pounds by 
cutting off the steam earlier in the stroke and thus save steam 
nearly in the proportion that the cut-off is reduced. A condenser 
can, therefore, either increase the capacity of an engine, or it will 
reduce its steam consumption per horse-power if the load and 
other conditions remain the same. If an engine is operated non- 
condensing with the most economical load for it and a condenser 
be fitted to the engine, this same load will no longer be the most 
economical one, although the steam consumption per horse-power 
per hour will probably be considerably less with the condenser 
than without it. A condensing engine should have a larger 
cylinder than a noncondensing engine to do the same work, if 
both are to run with the lowest possible steam consumption per 
horse-power. The method of determining proper cylinder dimen- 
sions for engines running condensing and noncondensing was 
given in Chapter IV. 

The attachment of a condenser to a turbine has the same effect 
that it has upon a steam engine in that it increases the work that 
may be obtained from the same quantity of steam, or, with a con- 
denser, less steam will be required to do the same work. There 
is opportunity for a condenser to save more with a turbine than 
with a steam engine, as it is possible to operate turbines with as 

141 



142 STEAM POWER PLANTS 

great a number of expansions of steam as possible, whereas, in a 
steam engine, the number of expansions is limited by cylinder 
condensation and the high cost of the large cylinder sizes neces- 
sary for a high number of expansions. 

A condenser provides means for bringing cool water into con- 
tact with exhaust steam or passing it through thin tubes around 
which the exhaust steam passes, so that the latter is condensed. 
A vacuum is formed in the condenser by reason of this condensa- 
tion, and thus part of the pressure of the atmosphere is removed. 
Because of the small volume occupied by the condensed steam 
relative to its volume as steam at the same temperature, con- 
densed steam or water may be removed from the condenser by 
a comparatively small pump using a small amount of power to 
operate it. This pump also removes such air as may be in the 
exhaust steam, hence it is usually called an air pump, although it 
serves to remove the water as well. 

Saving Due to Condensers. — Generally speaking, a condensing 
engine will use from 75 to 80 per cent of the steam required by 
a noncondensing engine. Power, however, is required to drive 
the air pump, and this saving is, therefore, not a net gain. The 
steam required to drive an independent steam-driven air pump 
and circulation pump is from 6 to 10 per cent of that used by the 
main engine, depending on the size of the latter. This use of 
steam for driving the air pump need not necessitate a loss, if the 
exhaust steam from the pump is used to warm the feed water 
before the latter is delivered to the boilers. If the feed water is 
drawn from the air-pump discharge or if it is fresh water heated 
in a feed-water heater placed in the exhaust pipe between the 
engine and condenser, 110° F. is about as high a feed temperature 
as can be obtained on account of the vacuum in the condenser and 
the correspondingly low temperature of the exhaust steam. It is, 
therefore, advantageous to use the steam exhausted by the con- 
denser pumps for feed-water heating in an auxiliary heater, so- 
called because it receives the exhaust steam of the auxiliaries of 
the plant, such as the condenser and boiler-feed pumps. This 
heater is sometimes called a secondary heater when a primary 
heater is placed in the exhaust pipe of the engine. By means of 
the auxiliary heater the feed water may be raised from 110 to 
about 180 degrees in a large, well-proportioned plant, and to a 
greater extent in smaller plants, as the steam required for the 



STEAM POWER PLANTS 143 

condenser pumps and boiler-feed pump becomes a greater pro- 
portion of that used by the main engine. 

With a noncondensing engine the feed water may be heated 
by the exhaust steam in a feed- water heater to within about 10 
degrees of the temperature of the steam or to about 200 degrees 
with steam at atmospheric pressure; consequently, with con- 
densing engines, the saving in coal used by the main engine due 
to a condenser over the use of the same engine running noncon- 
densing is partly counterbalanced by the higher feed temperature 
that may be secured when running noncondensing. With feed 
water taken from the condenser discharge at a temperature of 
110 degrees, there would be a saving, with a steam pressure of 
100 pounds, of about 9 per cent if the feed water could be further 
raised in temperature to about 205 degrees, as it probably could 
be if the engine was run noncondensing. However, by using the 
exhaust steam from the air and boiler-feed pumps of a condensing 
plant to warm the feed water taken from the air-pump discharge, 
there will be such a small difference between the final feed tem- 
peratures in the two types of plants that the slight difference 
can be neglected in considering the saving due to the use of a 
condenser. It is impossible, and perhaps unnecessary, to figure 
the exact saving a condenser will produce, but, generally speak- 
ing, it may be taken at about 20 per cent, hence plants are almost 
always fitted with these auxiliaries when condensing water is to 
be had, and the exhaust steam is not needed for heating or for 
some manufacturing purpose. When an abundant supply of con- 
densing water is not available, steam-plant owners often go to 
considerable expense for artificial cooling devices, so great is the 
economy in using condensers. 

Condensers. — With turbines the saving due to condensers is 
more marked than it is with a steam engine, the amount depend- 
ing upon the size of the turbine and the initial steam pressure. 
With turbines a very large part of the work done is due to the 
expansion of steam from atmospheric pressure down to the pres- 
sure of high vacuum, and there is a very marked change in the 
steam consumption due to increasing the vacuum from 27 to 28 
inches, the latter figure being common in turbine practice. The 
accompanying table (24), gives the steam consumption guaran- 
teed by the manufacturer of a 1000-kw. turbine operating with 
steam at 150 pounds gauge pressure under different conditions 
of load and vacuum. 



144 



STEAM POWER PLANTS 



TABLE 24. — STEAM CONSUMPTION. 



Vacuum. 


| load. 


f load. 


Full load. 


li load. 


27 
28 
29 


23.6 
21.9 
20.3 


21.0 
19.7 

18.4 


19.8 

18.7 
17.5 


20.75 

19.0 

17.7 



It will be noticed that at full load there is a reduction in the 
steam consumption of over 11 per cent due to increasing the 
vacuum from 27 inches to 29 inches. This, however, is not all 
net gain as a greater expenditure of fuel is required to maintain 
the higher vacuum. 

Type of Condenser. — Condensers may be divided into three 
general types, known as the jet, the surface, and the siphon or 
barometric condensers. Up to the advent of the turbine, con- 
densers were comparatively simple, the jet and surface condens- 
ers requiring an air pump either directly driven from the engine 
or driven by steam cylinders forming part of their equipment. 
Even with the barometric condensers a form of air pump known 
as a dry- vacuum pump was sometimes used with large engines. 
The direct-connected air pump is now seldom if ever used with 
engines for power purposes, the satisfactory manner in which 
the independent condensers have been perfected and their superi- 
ority over the direct-driven air pump having brought this about. 
The development of the steam turbine, requiring as it does a 
very high vacuum and the immense size of turbines, several 
units of 20,000 kw. having been manufactured, requiring a sup- 
ply of from 40,000 to 50,000 gallons of cooling water per minute, 
have completely revolutionized condenser practice, and all kinds 
of combinations have been brought out. 

The jet condenser in its simplest form usually consists of a 
pear-shaped chamber at the top of which the exhaust steam 
enters, while at one side is a connection for the injection or con- 
densing water. The bottom of the chamber has a contracted 
neck connecting with an air pump which is sometimes very 
similar to the ordinary direct-acting steam pump, or it may be 
an air pump of special design. A cross section of the Blake jet 
condenser with horizontal double-acting air pump is shown in 
Fig. 44. 



STEAM POWER PLANTS 



145 



The surface condenser consists of a shell, usually of cast iron, 
containing a large number of brass or copper pipes through which 
the condensing water is circulated, the exhaust steam being ad- 
mitted to the shell in the space surrounding the pipes. The 
steam coming in contact with the cooled pipes is condensed, and 
the condenser is so connected with the air pump that the con- 




Fig. 44. Section of Blake Jet Condenser. 



densed steam flows by gravity to the air pump, by which it is 
removed to maintain the vacuum. If the cooling water is under 
pressure no pump is necessary to circulate it through the con- 
denser. If not, a circulating pump is required and this may be 
driven by the same steam cylinder that operates the air pump. 
It is usually the practice in small condensers to place the air 
and circulating pump and the steam cylinder operating them in 
line, tandem, beneath the condenser and on a base supporting 
the whole. An arrangement of this kind showing the Wheeler 



146 



STEAM POWER PLANTS 



method of mounting a surface condenser on the cylinders of a 
Knowles' air and circulating pump is shown in Fig. 45. Cir- 
culating water is sometimes supplied by centrifugal pumps 
driven by an engine or electric motor. As the condensed steam 
does not come in contact with the circulating water in the surface 
condenser, this type can be used when the circulating water is 
of such a character that it should not be fed to the boilers. The 
condensed steam is used over again until it becomes so impreg- 
nated with cylinder oil from the engine that it has to be replaced 




Fig. 45. Knowles' Air and Circulating Pump. 



p-i^-i 



by fresh water. The presence of cylinder oil in feed water causes 
trouble in steam boilers, and it is the fear of this trouble from 
oil that prevents the wider adoption of the surface condenser in 
power plants. However, by providing proper filters of sand, 
cloth, sponges, excelsior, or similar material for the feed water 
and properly looking after them, there is no reason why the 
surface condenser cannot be used with success. In certain 
rivers which are sour and contaminated with sewage the surface 
condenser has proved to be very costly, due to the rapid deterio- 
ration of the tubes. 

Figure 46 shows in plan an elevation of a Worthington surface- 
condensing equipment as applied to a 3000-kw. Curtis turbine. 
Cooling water is supplied by an engine-driven centrifugal pump, 
and a motor-driven centrifugal pump draws the condensed steam 



STEAM POWER PLANTS 



147 




Up=f 



Fig. 46. Plan and Elevation of a Worthington Surface Condensing Equip- 
ment as applied to a 3000-kw. Curtis Turbine. 



148 



STEAM POWER PLANTS 



ffelier Yalvz 



from the hot well, while an engine-driven, dry -vacuum pump is 
also connected to the hot well. 

The Bulkley siphon condenser, which in a general way is sim- 
ilar to others of this type, is shown in Fig. 47. The steam from 

the engine is led in a pipe to the 
top of the condenser, which is ele- 
vated sufficiently to be placed about 
34 feet above the surface of a hot 
well into which the condenser dis- 
charges. The injection water enters 
at the side and mingles with the 
steam at the lower edge of the cone 
shown. By contracting the neck of 
the condenser below the cone, suffi- 
cient velocity is given the water in 
falling to the hot well to maintain 
a siphon-like action that draws the 
air and noncondensable vapors from 
the exhaust pipe, and causes a vac- 
uum to exist in it. The injection 
water can be supplied by a pump 
of either the steam-driven or the 
centrifugal type. If the injection 
water can be had under sufficient 
\ \_ 1 ^ verflc "* ' pressure, the pump is not necessary. 
This type of condenser will lift 
water from a source of supply, such 
as a tank or reservoir, through a 
height of 18 feet or less, but with 
this arrangement the siphon must 
be started. This can be done by 




Hof^el/. 

J 



Fig. 47. Siphon Condenser. 



running a horizontal pipe from the reservoir or tank across to 
a tee in the vertical discharge pipe of the condenser. Water 
flowing through this and down the discharge will gradually ex- 
haust the air from the upper part of the discharge pipe until 
sufficient vacuum is formed to draw the water up to the con- 
denser and start the water flowing through it. When this is 
done a valve in the cross connection or starting pipe is closed. 
Figure 48 shows an elevation of the Worthington elevated 
counter-current jet condenser which is a modification of the 



STEAM POWER PLANTS 



149 



Injection 



Air Suction 




Exhaust 
Inlet 



Tail Pipe 



Fig. 48. Elevation of the Worthington Elevated Counter-current Jet 

Condenser. 

siphon type. The condensing cone is considerably larger than 
in other siphon condensers, the idea being that the steam and 
water are more thoroughly mixed, thus using less water. The 
neck of the condenser is not contracted, as it is in the ordinary 
siphon condenser, to give the high velocity to the descending 



150 STEAM POWER PLANTS 

water necessary to suck the air down into the discharge or tail 
pipe. The contracted neck was avoided to give the water an 
unrestricted fall so that it could not by any chance back up in 
the condenser and run over into the exhaust pipe. To assist in 
removing the air from the condenser cone the top outlet is con- 
nected to a dry-vacuum pump, which constantly removes air 
from this pipe and very considerably increases the vacuum over 
what would be obtained without it. The entering cooling water 
falls down through the successive trays in a fine spray so as to 
hold it in a finely divided state in contact with the steam as long 
as possible. 

While the above describes briefly the various types of con- 
densers in their simplest forms they have been elaborated to a 
considerable extent. With turbines the power required to drive 
the various air and circulating pumps is so great that Corliss 
engines of the highest economy are frequently used for this 
purpose. The condenser for the 12,000 kw. with the Curtis ver- 
tical turbine in the Commonwealth Edison Company's station 
in Chicago is located beneath the turbine and forms a base for 
it. The impeller of the circulating pump is mounted on the end 
of the shaft of the Corliss engine driving it, and the air pump is 
placed in the rear of the engine cylinder, and is operated by a 
tail rod passing through the back head of the steam cylinder. 
In other cases the air pump is operated in a similar manner with 
a separate centrifugal pump furnishing the circulating water and 
driven at a higher rotative speed, either by a high-speed steam 
engine or by an electric motor or a steam turbine. A typical 
case of this kind was shown in Fig. 46. 

The jet type of condenser is less expensive than the surface 
and very excellent results have been obtained by connecting the 
discharge of the condenser directly into the suction of an engine- 
or motor-driven centrifugal pump with a separate dry-vacuum 
pump connected to the condenser head for removing the air. 

As to the relative advantages of different types of condensers 
the surface type is the most efficient, and it is possible to secure 
a higher vacuum with this type than with the others, the con- 
ditions being equally favorable. This is largely due to the fact 
that the cooling water does not come into direct contact with 
the steam, hence the air-removing apparatus does not have to 
remove the vapors from the cooling water. Furthermore they 



STEAM POWER PLANTS 151 

can, generally speaking, be located more favorably than other 
types as they can be connected directly to the discharge passage 
from certain types of turbines. 

Location of Condensers. — It is important to locate a con- 
denser of the jet or surface type on a lower level than the engine 
or turbine, so that the pipe connecting the engine and condenser 
will be either perfectly horizontal or pitch slightly toward the 
condenser. This is necessary to prevent the existence of a 
pocket where water can collect in the pipe line. As this pipe is 
under a vacuum, water due to condensation that collects in it 
cannot be drawn off by a trap. A vacuum trap might be used 
but it is advisable not to use one if possible. If a pocket does 
exist there is chance, in the event of broken vacuum, of this 
water getting back into the engine cylinder and wrecking it. One 
occasionally sees a condenser located on the floor with an engine. 
When this is done the exhaust pipe from the engine drops from 
the bottom of the cylinder, then runs horizontally, then rises 
to the condenser, thus forming a pocket, to which objection has 
been raised; this arrangement should be avoided. 

There being a vacuum in the condenser, the injection water 
can be lifted from a reservoir or pond at a lower level. It is not 
advisable to lift water through a greater head than 20 feet, in- 
cluding the actual vertical distance the water is raised and also 
the friction of the water in the injection or suction pipe. A con- 
denser is sometimes located in a pit considerably below the engine 
or turbine in order that the lift may not be too great. As stated 
in the first chapter of this series, the availability of a supply 
of condensing water often determines the location of the power 
house. If a river or reservoir is near by and it is not desirable 
to locate the power house close to the river, water can be led 
to a well close to the condenser either in an open trench or in a 
tunnel or conduit and the injection pipe run to the well. This 
would overcome the use of a long injection pipe. If the injection 
pipe is run underground it should not be covered over with earth 
until after the condenser is started and the pipe tested for air 
leaks. One of the most frequent causes of trouble with a con- 
denser is a leaky suction pipe, hence the greatest care should be 
used to make sure that it is perfectly tight. Various methods 
of connecting condensers with engines were given in the chapter 
on " Steam Piping." 



152 STEAM POWER PLANTS 

Water Necessary for Condensers. — A considerable amount of 
water must be available if a condenser be used, and to calculate 
this, one must first find the weight of water necessary to condense 
each pound of exhaust steam and then determine the amount 
necessary to condense all the steam exhausted by the engine or 
turbine. The former is found by dividing the rise in temperature 
that takes place in water used to condense the steam into the 
heat contained in one pound of steam at the pressure at which 
the exhaust valve in the engine begins to open less the heat in 
one pound of water at the temperature of the air-pump discharge. 
Expressed algebraically, this equation is: W = (H — h)-^-(T — t); 
in which H is the total heat in steam at the terminal pressure, 
h is the heat in water at the temperature of the air-pump dis- 
charge, T is the temperature of the discharge condensing water, 
and t is the temperature of the entering condensing water. The 
value of H for different pressures and temperatures may be 
found in tables giving the properties of saturated steam, and 
may usually be taken at 1150. Taking average values for a 
surface condenser with h at 120, T at 110, and t at 70, then W 
will be found to have a value of about 26 pounds per hour. If 
a jet condenser is used the condensed steam and air-pump dis- 
charge would have the same temperature. When the same 
water is used over and over again to condense with, as is done 
with cooling towers or cooling reservoirs, the temperature of the 
condensing water is quite high when it enters the condenser, so 
that each pound can absorb a comparatively small amount of 
heat, hence a correspondingly greater volume of condensing 
water is required. 

With turbines under 28 inches of vacuum and a cooling water 
temperature of 70 degrees in summer, average practice is to so 
design the condensing system that the circulating water when 
leaving the condenser will be within at least 15 degrees of the 
temperature of the steam entering the condenser and an increase 
in the temperature of the cooling water of at least 15 degrees. 
As the total heat in steam at 1 pound absolute pressure is 1145, 
and as k would have a value of 101, T would have a value of 86 
and t a value of 7.0 Hence the amount of cooling water required 
would be a little over 65 pounds per pound of steam condensed. 
If the amount of cooling water is increased the amount of surface 
required in a surface condenser could be decreased, but at an 




I Vertical Section. 
Chimney, Lincoln Wharf Station, Boston 
Elevated Railway Company, 
george a. kimball, ch. eng'r. 



Vertical Section. 



Chimney for U. S. Government, Manila, P. I. 

F. L. STRONG, CON. ENg'r; EDWARD BARROIH, ARCH. 



Plate 15. 



STEAM POWER PLANTS 153 

expense of the greater amount of power required to drive the 
circulating pump. Again if the volume of water is decreased the 
discharge water would be of a higher temperature, hence the dif- 
ference between the mean water temperature and the steam would 
be less and a greater surface would be required in the condenser. 

In estimating the quantity of injection water necessary, due 
consideration should be given the amount of steam exhausted by 
the engine or turbine during maximum load. The author be- 
lieves in being very liberal in selecting condensers, for a good 
vacuum, particularly with engines operating with low mean 
effective pressures, is conducive to high economy. With turbines 
a good vacuum is imperative. Some engineers hold that a high 
vacuum with engines is a mistake, one of the reasons being that 
with it the temperature of the condenser discharge is lower and 
consequently the feed water will not be so hot. There is, how- 
ever, a loss due to reducing the mean effective pressure acting on 
the engine piston that considerably more than offsets such a gain. 
By a decrease in the vacuum from 26 to 24 inches it would be 
impossible to increase the feed- water temperature more than 15 
degrees, and this would mean a saving of a little more than 1 
per cent. This decrease in vacuum in a compound engine, with 
125 pounds steam pressure, most economically loaded would 
effect, theoretically, an increase in the steam used of about 5 or 6 
per cent, and with a simple engine about 2.5 per cent. It will be 
noticed on investigating duty trials of large pumping engines, 
where high duty is desired, that a very high vacuum is sought by 
the builder. The effect of condensers upon steam turbines is 
discussed briefly in the chapter on " Turbines." 

Sources of Water Supply for Condensers. — Water for con- 
densing purposes may be obtained from rivers, in which event the 
water goes to waste after it is discharged from the condensers, 
or from ponds or artificial reservoirs. When drawn from ponds 
or artificial reservoirs the source of supply has to have sufficient 
volume and surface so that it will be cooled naturally by the air. 
If the reservoir is too small for this it must be cooled artificially 
by some method that exposes the water sufficiently to the air to 
cool it, as in the cooling tower. Reservoirs where the cooling is 
done naturally require surface sufficiently large to allow enough 
water to come in contact with the air to remove the necessary 
amount of heat from it, and they should also have sufficient vol- 



154 STEAM POWER PLANTS 

ume, if they are used continuously, so that the water can remain 
in the reservoir long enough to be cooled before being used again. 
Cooling reservoirs of this kind are rendered much more efficient 
by dividing them by partition walls so that the water is compelled 
to travel some distance in passing from the condenser discharge 
to the intake where it is drawn from the reservoir to return to 
the condenser. This is to prevent the discharge from the con- 
denser from immediately entering the intake, or short-circuiting, 
before it has time to cool. 

There is very little reliable information on the surface and 
volume required in cooling reservoirs. Thomas Box, in his work 
on " Heat," says that when an engine works day and night the 
depth of the reservoir is unimportant, and that 210 square feet of 
surface is required per horse-power. When an engine runs only 
12 hours per day the surface may be reduced to 105 square feet 
per horse-power, but in the latter case the depth of the reservoir 
must be such as to give 300 cubic feet per horse-power. Box 
assumes the use of one cubic foot or 62J pounds of water evapo- 
rated into steam per horse-power. These data are based on ex- 
periments when the water was reduced in temperature from 122° 
to 82° F., the air being at a temperature of 52 degrees and the 
humidity 85 per cent. 

Cooling Towers. — These appliances provide means for arti- 
ficially cooling condensing water, and their successful develop- 
ment has made it possible to obtain the benefit of a condenser in 
many plants where condensers would be out of the question with- 
out them. Usually they consist of large cylinders of sheet steel 
open at the top and enclosing either mats or tiles or some similar 
substance presenting a large surface over which the hot water 
from the condensers is allowed to trickle downward, from dis- 
tributing pipes at the top. The water falls into a reservoir at the 
bottom, from which it is returned to the condenser. An opening 
or openings in the side of the tower allow the air to enter and pass 
up through it, thus cooling the water. Usually a fan driven by 
an electric motor or small steam engine is used to stimulate this 
current of air. A cooling tower can be located almost anywhere 
outside of a power house, on the ground or on the roof. There 
is a loss of circulating water attending their use of from 10 to 15 
per cent of that passing through them, owing to the evaporation 
that occurs. This, however, is more than made up, with jet con- 



STEAM POWER PLANTS 



155 



densers, by the discharge from the air pump of the condensed 
steam. Where cooling towers are located at a higher elevation 
than the engine, the condensing water must be pumped from the 
condenser to the tower, but the power required to do this is, 




CIRCULATING PUMP • 



HOT WELL 



COLD WATER 



Fig. 49. Alberger Cooling Tower. 

with surface condensers, partly counterbalanced by the fall of 
water from the reservoir at the base of the tower to the condenser. 
The column of water in the condenser discharge pipe for the 
height of the tower itself is, of course, unbalanced. A view of 
an Alberger cooling tower as applied to a surface condenser for 
a turbine is shown in Fig. 49. 



156 STEAM POWER PLANTS 

Specifications for Condensers. — Generally in purchasing jet 
condensers for an engine an engineer states the horse-power and 
type of engine for which a condenser is wanted, but it is better, 
perhaps, if the engineer is sure it will be correct, to give the num- 
ber of pounds of steam that must be condensed in a given time, 
and the vacuum that is desired. This is usually 26 inches in 
engines. Specifications should also call for a blue-print or draw- 
ing showing the condenser the builder intends to supply, and on 
this blue-print should be given the outside dimensions of the con- 
denser, the size of the steam cylinder, the diameter and location 
of steam- and exhaust-pipe openings, the injection or suction pipe, 
and the discharge pipe. The delivery and erection of the con- 
denser should be provided for, if the builder is to deliver and 
install it. 

A specification for a surface condenser with combined air and 
circulating pumps should ask for a print of the apparatus, the 
size of the air, water, and steam cylinders, the size of the steam 
and exhaust pipes, etc., also the square feet of heating surface 
in the condenser proper. 

When it comes to buying a condenser for a turbine plant the 
advice of reliable and experienced firms manufacturing condensers 
for this class of work should be obtained. In this case the engi- 
neer had better let the contractors submit their own plans and 
specifications. 

Guarantees. — Sometimes a condenser manufacturer is re- 
quired to guarantee its efficiency, but this is not often done. The 
form of guarantee that is fairest to the manufacturer would be, 
perhaps, to ask that the apparatus with an air-pump piston speed 
not exceeding a specified amount, should condense a given amount 
of steam delivered to it at a certain pressure, and maintain the 
required vacuum, with a given temperature of cooling water. 
The location at which the vacuum is to be obtained should be 
stated, for frequently there is considerable drop in pressure 
between the exhaust pipe next to the engine and the condenser, 
owing to a too long or too small exhaust pipe. The vacuum 
ought to be measured close to the condenser, for the maker of 
the latter may not be responsible for the selection of the exhaust 
pipe. He may not be responsible for the size and run of the 
injection pipe leading cold water to the condenser, or for the 
lift of water in it, and as these very materially affect the efficiency 



STEAM POWER PLANTS 157 

of the condenser, the manufacturer should have the opportunity, 
if a guarantee is made, to approve the details, size, and arrange- 
ment of the injection pipes. These remarks apply also to jet and 
siphon condensers. With a surface condenser and combined air 
and circulating pumps, the only guarantee that should be asked 
is maintaining a specified vacuum with a piston speed of the air 
pump not exceeding a specified amount and a specified tempera- 
ture of cooling water. The manufacturer would have to satisfy 
himself with the arrangement of the water piping that it was pro- 
posed to use. If a complete cooling tower and condensing outfit 
was to be supplied the guarantee should state the vacuum that is 
to be obtained with a given temperature of outside air, and when 
that air contains a certain percentage of moisture. 

Boiler-feed Pumps. — Boiler-feed pumps may be of two gen- 
eral types, the direct-acting steam pump and some multi-stage 
form of centrifugal pump, the latter driven either by an elec- 
trical motor or by a steam turbine. Centrifugal pumps are 
used quite successfully in very large power stations and they are 
generally turbine-driven. The direct-acting boiler-feed pump 
may be the ordinary piston-pattern pump, the outside center- 
packed-plunger pump or the outside end-packed-plunger pump. 
Plunger pumps may be easily packed without opening up the 
pump chambers. The piston pump is the cheapest and the end- 
packed pump the most expensive and likewise the best for high 
pressures and large pumps. Again, a pump may have valves in 
the pump chamber or the pump may have the more accessible 
pot valves. The pot type of valves are much more accessible. 

The center-packed-plunger pump has four separate water 
chambers for the purpose of reducing the expense of replacement 
should damage occur. The piston pump requires less space and 
the outside-end-packed the most space. In the pot valve end- 
packed water end there are four cylinders, two on each side, cast 
together with a diaphragm in the center. Four single-acting 
plungers work in the ends of these through stuffing boxes, the 
plungers on each side being connected together by crossheads 
and tie-rods; thus no piston rod enters the water cylinders. 
The chambers are cast separate from water cylinders and the 
suctions and discharge valves may be gotten at without dis- 
turbing any part of the water end. Sectional views of the end- 
packed pot-valve pump are shown in Fig. 50. 



158 



STEAM POWER PLANTS 




STEAM POWER PLANTS 159 

For building work for boiler plants of 500 horse-power and 
under the piston pump is usually used, and in order that it will 
pump hot water the pump should be brass fitted, that is, provided 
with brass valves, pistons, and bronze piston rods with piston 
operating in brass-lined cylinders and brass stuffing boxes. With 
the plunger pumps the plunger is made, even for hot water, of a 
hard cast iron. Compound steam ends are seldom used on boiler- 
feed pumps except in very large plants. 



CHAPTER X. 

FEED-WATER HEATERS AND ECONOMIZERS. 

Value of Feed-water Heaters. — Exhaust-steam feed-water 
heaters are used to heat the water fed to boilers with steam ex- 
hausted by engines and pumps, and the saving due to their use 
is so great that plants are seldom constructed without them. 
Generally speaking, for every 11 degrees that feed water is 
warmed there is a saving of 1 per cent in the fuel burned. With 
sufficient exhaust steam available, cold feed water at 70° F. can 
be raised in temperature to 200 degrees, thus saving nearly 12 
per cent of the fuel. The heater will in many locations, there- 
fore, reduce the fuel consumption enough to pay for itself in a 
few months, the exact time depending upon the cost of the fuel. 

Types of Heaters. — Exhaust-steam feed-water heaters are of 
two types, the open and the closed. In the former, the heater 
consists of a box-like receptacle of cast iron or boiler steel to 
which the exhaust steam is led so as to fill its interior. The cold 
feed water is admitted at the top and in most designs trickles to 
the bottom over a series of trays and is thus brought in contact 
with the steam and is heated by it. If the water contains scale- 
forming salts which are precipitated at temperatures below 200 
degrees, they collect on the trays, which are removable for clean- 
ing. This type of heater sometimes has a filter in its base for 
further removing these precipitated salts and impurities that can 
be intercepted by filtration. The feed water is drawn from a 
point near the bottom of the heater and pumped to the boilers. 
The pump must be located so as to receive the water under 
pressure, as it will not lift the water if it is under a high tempera- 
ture. The condensation from heating systems, the discharge 
from traps connected to high-pressure drips, engine jackets,; 
reheaters, etc., which are to be returned to the boilers, can be 
connected to a heater of this type. A certain water level is 
maintained in the heater, and to do this the supply of cold feed 
water is controlled by a valve operated by a float in the heater, 

160 




IQyv,-»i5^-fxfto«sf Mam. 



i £na>nicM*o RECORO. 



' T ' fflfi i t 




E E«ommbi*o RECOH") 



Plate 16. — La Bella Power Plant, Goldfleld, Cal. 

l. t. summers, engineer. 



STEAM POWER PLANTS 161 

so that cold water is admitted when the boiler-feed pump draws 
water from it faster than it is supplied by the heating returns, 
drips, etc. An overflow controlled by a valve operated by a float 
in the heater is also provided. It is absolutely essential that an 
efficient grease separator be placed in the steam pipe leading to 
an open heater, so that oil cannot enter it and pass on to the 
boilers mixed with the feed water. 

Closed heaters usually consist of a cylindrical shell of cast iron 
or boiler steel containing tubes extending from one head to the 
other, or coils of pipe. Sometimes the exhaust steam is admitted 
to the shell so as to surround the pipes or coils containing the 
feed water, in which event the heater is said to be of the water- 
tube type. If the steam is inside of the coils with the water 
surrounding them, it is a steam-tube heater. Closed feed-water 
heaters are usually supplied with a steam inlet and outlet, al- 
though they are sometimes arranged with only a single connec- 
tion, reliance being placed on the vacuum that forms in the 
heater when steam is condensed to cause more steam to flow into 
it. As a certain amount of air exists in the exhaust steam, this 
will find its way into the heater and is apt to impair its efficiency. 
For that reason many engineers believe that there should be a 
double-steam connection, unless some means of removing the 
air is provided, to prevent air from accumulating and thus to 
insure a thorough circulation of steam through the heater. Ex- 
perience has shown in water-tube heaters that the best results 
are obtained when the water is compelled to pass through the 
tubes successively, for the reason that the velocity of the water 
per unit of heating surface is greater. The multipass heater 
is the outcome of this experience. Closed heaters are made to 
rest in a horizontal or vertical position. The latter are to be 
preferred if it is convenient to use them, as they take up much 
less floor area and the circulation of water in them is much more 
thorough unless the tubes are subdivided into groups. 

Uses for Heaters. — The manner in which feed-water heaters 
are used depends upon the type of plant in which they are in- 
stalled. With noncondensing engines, where the exhaust steam 
is available for feed-water heating, the feed water may be raised 
to a temperature of about 205° F. ; and when this is done, it is 
usually the custom to allow one square foot of heating surface 
in brass or copper pipes for every 90 pounds of water passed 



162 STEAM POWER PLANTS 

through the heater per hour. With condensing engines it is 
sometimes the practice to place a feed-water heater of the closed 
type in the exhaust pipe of the engine, unless two different sets 
of conditions exist. If the air pumps and boiler-feed pumps are 
steam driven, and the steam exhausted by them added to the 
steam exhausted by all other pumps or steam auxiliaries in the 
plant amounts to one-seventh or more of the steam generated in 
the boilers, this exhaust steam from the auxiliaries can be led to 
an auxiliary feed-water heater and the feed water warmed by it 
from about 75 to about 205 degrees. In this event, a heater in 
the exhaust pipe of the engine would be of no value; nor would 
it, if the feed water were drawn from the condenser discharge, 
for in that event it would be at nearly as high a temperature as 
the exhaust steam from the main engine, so that it would hardly 
pay to attempt to use this steam for heating. The exhaust steam 
from the main engine being under a partial vacuum, say 26 
inches, would have a temperature of about 125 degrees, and the 
condenser discharge probably about 100 degrees. If the exhaust 
steam from the auxiliaries be not sufficient in quantity to raise 
the feed water from a temperature of 60 or 70 degrees to about 
205 degrees, then a feed-water heater can be placed in the ex- 
haust pipe of the engine and the water warmed from the lower 
temperature to about 115 degrees and finally passed through 
an auxiliary heater and there warmed to as high a temperature 
as possible with the auxiliary exhaust steam available. This 
auxiliary heater is almost invariably used in the latest plants 
while only occasionally is a heater placed in the main exhaust 
pipe of a condensing engine. Auxiliary heaters of the closed type 
should have the same amount of heating surface as heaters 
receiving steam at atmospheric pressure. This rating was pre- 
viously given. Heaters placed in the exhaust pipes of condens- 
ing engines should have more surface, usually one square foot 
for every 60 pounds of water passed through the heater per hour, 
this being necessary because the difference between the temper- 
ature of the steam and the mean water temperature is less than 
it is with heaters using steam at atmospheric pressure. 

Condensation in Heaters. — The condensation that occurs in 
a feed-water heater amounts to about one-seventh of the weight 
of the feed water passing through the heater, when the water is 
raised from 70 to about 205 degrees. In an open heater this, of 



STEAM POWER PLANTS 163 

course, mingles with the feed water and passes on to the boilers 
with it. In a closed heater, the steam not being in contact with 
the water, the condensation occurring has to be removed from 
the heater, and this can be done by leading it to a steam trap. 
It should not be forgotten that the steam pressure in a heater is 
frequently at practically the same pressure as the atmosphere, 
hence the discharge from the trap should be carried downward, 
or on a level rather than upward, as there is no pressure to lift 
the water. It is not necessary to save the condensation in a 
closed heater unless the cost of this water which, as has been said, 
is about one-seventh of the total feed water, is sufficient to make 
the saving of it advisable; or unless there is not enough exhaust 
steam to warm the feed water to as high a temperature as may 
be possible. If there is plenty of exhaust steam, that would 
otherwise go to waste, available for heating, the heat in this con- 
densation in the heater is of no value. If the condensation from 
a closed feed-water heater is to be returned to the boilers, it 
should be trapped, and the discharge from the trap led to a re- 
ceiving tank combined with a pump controlled by the level of 
the water in the tank. Other drips from cylinder jackets, high- 
pressure steam pipes, reheating receivers, etc., can also be led to 
this tank, each discharging through a trap, or the condensation 
can be returned to the boilers direct by the steam loop or the 
Holly system. 

Purchasing Heaters. — In purchasing a feed-water heater for 
a power plant for a manufacturing or electric company, the 
heater is usually purchased by the owner direct, although in 
some plants, notably those in office buildings, the purchase, 
delivery, and installation of the feed-water heater is frequently 
included in the specifications for the piping. The writer believes 
that it is much better to make the purchase of the heater a 
separate contract. The specifications for a closed heater should 
state the amount of heating surface required, the kind of metal 
that the tubes are to be made of, whether it is to be of the steam 
or water-tube type, and horizontal or vertical. If the supplying 
and installation of the heater is to be made part of the contract 
for the steam piping or some other part of the plant, the con- 
tractor undertaking it should be required to deliver and erect it. 
If the heater is to be purchased direct from its manufacturers, 
the specifications should ask that the bids cover the delivery of 



164 STEAM POWER PLANTS 

the heater free on board cars at the nearest railway point to 
the power plant. The specifications should ask each bidder to 
furnish a blue-print or drawing showing the details of the con- 
struction of the heater it is proposed to furnish, its exact dimen- 
sions and the location of the steam and water outlets and their 
sizes. 

There is no general rule that the writer is aware of for pro- 
portioning heaters of the open type. Therefore a specification 
for a heater of this kind should state the quantity of water to be 
passed through the heater in a given time and also the initial 
temperature of the water and the final temperature desired. A 
print or drawing of the heater a bidder is to provide should be 
obtained and the inside dimensions of the heater, the volume of 
the steam and water space, etc., should be investigated. The 
heater must not be too small, otherwise the water in passing 
through it cannot be broken up in sufficiently small particles to 
allow the water to mix thoroughly with the steam and thus be 
sufficiently heated by it. If a guarantee as to the efficiency of a 
feed-water heater is required, it should be in the following form : 

The maker guarantees the heater to be capable of warming ■ 

pounds of water per hour from a temperature of- degrees F. 

to degrees F. with sufficient steam at atmospheric pressure. 

Economizers. — Economizers are used in connection with 
steam boilers to warm water either for boiler feeding or for some 
manufacturing purpose, by the heat in the gases from boilers that 
would otherwise go to waste. Economizers are also useful in 
increasing the capacity of a boiler plant already in operation, in 
providing means for storing a large quantity of water at high 
temperatures, which is of advantage in the event of a sudden 
increase in the demand for steam. They also deliver the water to 
boilers at high temperature and reduce strains in boilers due to 
the admission of cold water. One disadvantage of economizers 
is that they reduce the draft slightly owing to the friction of the 
gases passing through them and to the reductioji in temperature 
of the gases. Provision should be made for this by the use of 
mechanical draft or of larger chimneys than would be necessary 
if economizers are not used. In plants already constructed the 
addition of economizers reduces the coal consumption, and this 
counterbalances in a measure the loss in draft, as less draft is 
necessary with them because less fuel is burned. 



STEAM POWER PLANTS 



165 



Economizers consist of vertical cast-iron pipes about 4 inches 
in diameter and 9 feet long placed in rows several inches apart, 
each row being connected at the top and bottom to cast-iron head- 
ers through which the water is supplied and withdrawn. They 
are provided with scrapers that encircle the pipes and that are 




B — 



Z'Anchor Bolts. 



-B 



'Clean-Out Doors- 
Sectional Plcin on Lin© C-C, 



I-BeomUnM. 



5, * \y* s; ! ijS'i'in'n '!»' > 



O radel Line, ) 




Longitudinal Section B-B- 



Fig. 51. 



Economizer Arrangement, Plant of Schwarzchild and Sulzberger, 
Chicago, 111. (L. Levy, Chief Engineer.) 



continuously raised and lowered by a suitable mechanism, the 
power coming usually from a small steam engine. Economizers 
are placed in brick flues between the boilers and the chimney, and 
a by-pass flue must be provided for use when the economizer is 
out of service, either for cleaning, which is necessary at intervals, 
or for repairs. Economizers are used to a very considerable 
extent in Europe, more so in fact than in the United States, where 



166 STEAM POWER PLANTS 

engineers are now, however, rapidly appreciating their advan- 
tages. When first introduced, a number of failures occurred 
mainly due to improper design. They were then either con- 
structed of poor materials improperly put together or there was a 
lack of sufficient heating surface necessary to make the saving 
that they should produce. Since the economizer has been per- 
fected and made of durable materials, their advantages have 
become recognized. 

The heating surface in economizers takes the place, in a meas- 
ure, of additional boiler-heating surface. If a boiler is operating 
under certain conditions so that, with a certain rate of evapora- 
tion per square foot of heating surface, a certain temperature of 
waste gases follows, it would be possible to add more heating 
surface and abstract more heat from these gases ; but the boiler- 
heating surface would not be so efficient in doing this as an equiv- 
alent amount of economizer surface, for the reason that the 
average temperature of the water in the economizer is lower than 
that of the water in the boiler; this causes a more rapid transfer 
of heat from the gases to the water in the economizers than there 
would be from the gases to the water in the boiler. The saving 
that an economizer can produce increases as the flue temperature 
increases because there is more heat for it to absorb. An econo- 
mizer can only heat the water to a given point, hence as the 
temperature of the entering water increases, due to previous 
heating, as in an exhaust steam heater, the saving possible with 
the economizer becomes less. If the ratio of boiler-heating sur- 
face to the amount of coal burned is such that as much of the heat 
in the waste gases is absorbed as is possible, there is not as much 
heat left in the gases for the economizers to save as there would be 
if the ratio of boiler-heating surface to the amount of coal burned 
were less. Barrus, in his book on " Boiler Tests," states in effect 
that where a boiler is operated most efficiently, the temperature 
of the waste gases should not exceed about 400° F., and boilers 
are usually so proportioned that about this temperature exists 
when the highest efficiency is attained. Owing, however, to the 
accumulation of soot upon the boiler surface or to running at a 
higher rate of evaporation than the normal, the temperature of 
the waste gases usually exceeds that given, so that an economizer 
is valuable in even a well-proportioned boiler plant. Mr. Barrus 
gives some excellent data showing the saving made by economiz- 



STEAM POWER PLANTS 



167 



ers with low temperatures of flue gases, and they are reproduced 
in Table 25, herewith. 

TABLE 25. — BARRUS' TESTS OF ECONOMIZERS. 



Heating surface, boiler, sq. ft 

Heating surface, economizer, sq. ft 

Temperature of gases leaving boiler, deg 

Temperature of gases leaving economizer, deg. 

Temperature of feed water entering econo- 
mizer, deg 

Temperature of feed water entering boiler, deg. 

Increased evaporation produced by econo- 
mizer, per cent 



1894 


1058 


5592 


3126 


1600 


1920 


1280 


1600 


376 


361 


403 


435 


231 


254 


299 


279 


95 


79 


111 


84 


175 


145 


169 


196 


10.5 


7 


9.3 


12.8 



Mr. William R. Roney, in a paper on " Mechanical Draft " 
(Transactions, Am. Soc. M. E., Vol. XV), gives some additional 
data on the saving due to economizers working under various 
conditions in nine different plants. They are given in Table 26. 

TABLE 26. — RONEY'S TESTS OF ECONOMIZERS. 



Plants tested 

Gases entering economizer, deg. 
Gases leaving economizer, deg. 
Water entering economizer, deg. 
Water leaving economizer, deg. 
Gain in temperature of water, 

deg 

Fuel saving, per cent 



1 


2 


3 


4 


5 


6 


7 


8 


9 


610 


505 


550 


522 


505 


465 


490 


495 


595 


340 


212 


205 


320 


320 


250 


290 


190 


299 


110 


84 


185 


155 


190 


180 


165 


155 


130 


287 


276 


305 


300 


300 


295 


280 


320 


311 


117 


192 


120 


145 


110 


115 


115 


165 


181 


16.7 


17.1 


11.7 


13.8 


10.7 


11.2 


11.0 


15.5 


16.8 



In considering the saving that an economizer produces it is 
necessary to take into account the interest on the investment and 
the cost of repairs, cleaning, etc. Economizers cost, it is said, 
about $5.40 per boiler horse-power for plants of 1000 boiler horse- 
power or over, on the basis of 4.8 square feet of economizer sur- 
face per boiler horse-power. This includes the cost of the brick 
setting, delivering, and erecting, etc. Three per cent of the in- 
vestment will probably do more than pay for the cost of the 
operation, cleaning, and repairs. Assume a 1000-horse-power 
boiler plant to operate 300 ten-hour days per year, that the coal 
consumption is 3| pounds per boiler horse-power per hour and 
that coal costs $3 per ton of 2000 pounds delivered. The annual 
fuel cost would then be $15,750, and if an economizer reduced 
this by 12 per cent, then the saving that an economizer would 



168 STEAM POWER PLANTS 

produce would be $1890. The cost of the economizer at $5.40 
per boiler horse-power would be $5400 and 8 per cent of this 
for interest, repairs, operating, and cleaning is $432. Deducting 
$432 from $1890 would leave a net saving of $1458, which is 
sufficient to pay for the economizer in less than four years. If 
the plant was operated continuously, the annual fuel cost would 
be $45,990 and the net saving $5085, sufficient to pay for the 
economizer in about one year. The 12 per cent that was assumed 
in the previous calculations is a conservative estimate for the sav- 
ing with a low temperature of feed water. In the four tests made 
by Mr. Barrus, previously noted, the average saving was 9.9 per 
cent and this was obtained with unusually low temperatures of 
the escaping gases, due partly to the low-steam pressure under 
which the plants were operated, these varying in the different 
tests from 68 to 82 pounds. Economizer makers will guarantee 
that they can produce a saving of 6J per cent when the tempera- 
ture of the water entering them is as high as 200 degrees, the 
economizers having 4.5 square feet of heating surface per boiler 
horse-power and the boilers working at their normal rating. 




Company, Reading, Pa. 




Plate 17. — Longitudinal Section Through Boiler Room, Metropolitan Electric Company, Reading, Pa. 

WALTER J. JONES, CONSULTING ENGINEER, NEW YORK. 



CHAPTER XI. 
MECHANICAL DRAFT. 

Theory of Combustion. — As pointed out in a previous chapter, 
there are two independent factors that effect the efficiency of a 
steam boiler. One is the efficiency of the heating surface or its 
ability to transmit to the water the heat to which it is exposed, 
and the other is the efficiency of the furnace, by which is meant 
the amount of heat actually contained in each unit volume of fur- 
nace gas compared to that theoretically possible of attainment. 
A high surface efficiency demands that the temperature of the 
gases in contact with the boiler be as high as possible, for the rate 
of heat transfer is some function of the difference in temperature 
of the water and gases, and the greater the difference the more 
heat per unit of surface will be transmitted. A high furnace 
efficiency demands that just the proper amount ©f air be supplied 
to the furnace per pound of fuel burned. Too little air, due to a 
too thick bed of fuel on the grate in proportion to the available 
draft, results in loss due to the incomplete combustion of the 
fuel, part of the carbon being burned only to carbonic oxide 
instead of to carbonic acid, as it should if the combustion is 
complete. Too much air, on the other hand, due to too thin a 
bed of fuel, lowers the temperature of the furnace gases and 
thereby decreases the heat transferred per unit of heating surface, 
owing to the smaller difference between the gas and the water 
temperatures; it also increases the volume of gases and this in 
turn necessarily increases the velocity of their flow through the 
passages of the boiler, thus giving less time for their heat to be 
absorbed. 

A thin fire allows an excess of air to enter the furnace, while 
a thick fire tends to reduce it on account of the greater resistance 
offered. Mr. Walter B. Snow writes as follows in explaining 
the higher efficiency of a high rate of combustion: " If the size 
of a grate is reduced but the same amount of fuel burned by 
increasing the rate of combustion, the diminished area of the 

169 



170 STEAM POWER PLANTS 

grate and of the exposed interstices between the fuel necessitates 
a higher velocity to secure the admission of a given volume of 
air. This increased velocity in turn requires greater draft or air 
pressure. The volume at any given temperature passing through 
the coal is proportional to the velocity, but the pressure varies as 
the square of the velocity. Therefore, if a given grate be reduced 
one-half and the rate of combustion doubled, so as to maintain 
the same total consumption, the same volume of air would have 
to travel through the exposed interstices at twice the velocity. 
But the pressure or vacuum would be four times as great, and, 
as a consequence, the air would be forced or drawn into spaces 
between the fuel which it could not reach under lesser impelling 
force. Much more intimate contact and distribution are the 
results. Less free oxygen passes through the fuel bed uncon- 
sumed, and for a given supply of air a higher efficiency of the 
fuel is attained." Most leading authorities unite in the belief 
that a higher efficiency is secured in steam boilers when operat- 
ing at comparatively high rates of combustion. It is advisable 
to provide for this in plants using coal that can be burned rapidly, 
care being taken at the same time to provide sufficient draft to 
run the boilers over their normal rating when occasion demands. 
Certain coals high in ash and in sulphur cannot be burned at 
more than ordinary rates for reasons explained in Chapter II in 
the section relating to coals. 

Necessity for Ample Draft. — Means for providing a strong 
draft for steam boilers is one of the most essential features of a 
plant, for if sufficient coal can -be burned a boiler will generate 
steam several times as rapidly as under normal conditions. This 
means that a smaller number of the boilers can be relied upon to 
furnish the steam required, while others are shut down for re- 
pairs or cleaning, than would be needed if less draft was avail- 
able. The investment for boilers, therefore, need not be so 
great. Of course, when making steam at abnormally high rates 
of evaporation, the efficiency is not so good as under the condi- 
tions of normal working, but it is cheaper to allow some fuel to 
go to waste occasionally than to spend more money in the first 
place for boilers only used at long intervals. More complaints 
with steam boilers are probably traceable to insufficient draft 
than to any other cause. Draft is secured by a chimney, by 
mechanical draft produced by fans, or by steam-jet blowers. 



STEAM POWER PLANTS 171 

Mechanical Draft. — Mechanical draft may be secured by two 
methods, known as induced draft and forced draft. In the for- 
mer, a fan is connected with the smoke flue from a boiler or 
batteries of boilers, so as to suck the gases through the furnace, 
gas passages, and flues to the fan, which discharges it usually 
through a short chimney, but sometimes through a high one. 
Forced draft is the term applied to that system where air is forced 
into the furnace beneath the grate bars, either by a fan or by a 
steam-jet blower. The objection to forced draft lies in the fact 
that a pressure greater than that of the atmosphere is created 
in the furnace and gas passages which may cause the gas to pass 
outward through cracks in the setting of boilers and through the 
fire doors when the fires are being replenished or cleaned. Damp- 
ers in the blast pipe to the ashpit, to be closed when the fire 
doors are opened, may overcome this latter objection. With 
induced draft the leakage through the doors and brickwork is 
of course inward. Both induced draft and forced draft are used 
to a considerable extent, the choice usually depending upon 
which is the cheapest and easiest to install. 

Steam-jet blowers in which a jet of steam is relied upon to 
induce a flow of air into the ashpit of a boiler can only produce 
a moderate draft. Their steam is believed to be useful in pre- 
venting clinker from forming on the grates with certain kinds 
of anthracite coals. Steam jets are used to a considerable, but 
decreasing, extent in the anthracite coal regions. They can 
oftentimes be applied to existing plants with advantage, where 
mechanical draft would be difficult to install. Experiments 
made by a Board of Steam Engineers of the Navy Department 
with five different types of steam jets showed that they used 
from 8.3 to 21.2 per cent of the steam generated in the boiler 
to which the jets were applied. Draft can be obtained from fans 
with only a fractional part of these amounts. Under ordinary 
conditions a fan for mechanical draft can be driven by from 1 to 
5 per cent of the steam evaporated in the boilers operating under 
ordinary conditions, depending upon the size of the plant. 

Advantages of Mechanical Draft. — Draft produced by fans 
possesses many advantages over chimneys as ordinarily propor- 
tioned. Probably the greatest of these is its flexibility, it being 
possible to regulate the speed of the fan so that the proper rate 
of combustion for the amount of steam required is maintained 



172 



STEAM POWER PLANTS 



entirely independent of the weather conditions; another im- 
portant advantage is the ability of the fans to create a much 
greater draft than is possible with a chimney. Steam engines 
for driving fans are frequently fitted with valves arranged to 
govern the speed of the engine according as the boiler pressure 




Fig. 52. Power House, Olympia Mills, Columbia, S. C. 
(M. B. Smith-Whaley, Engineer.) 



varies, increasing it as the pressure falls and reducing it as it 
rises above the normal. Mechanical draft enables economizers 
to be placed in the flue and reduce the temperature of the escap- 
ing gases, by heating the feed water, far below the temperature 
that is necessary in a chimney to create a draft. The reduction 
in draft due to the use of economizers is a much greater per- 



STEAM POWER PLANTS 173 

centage of the available draft with a chimney than it is of the 
draft where fans are employed. Again, the greater draft of fans 
enables cheap low-grade fuels to be burned that could not easily 
be used with the chimney draft, and the saving that these fuels 
brings about in some localities is a very considerable sum of 
money. Still another point in favor of mechanical draft lies 
in the portability of the fans in case a change of location is 
desired. 

Theory of Fans. — Before explaining the method of selecting 
a fan for a given service it is necessary to consider briefly their 
theory of operation. Fans for mechanical draft are invariably 
of the centrifugal type and consist of a paddle wheel revolving 
in a sheet-iron casing, the air entering an opening in the casing 
at the axis of the wheel and being propelled radially to the casing 
by the action of centrifugal force, finally escaping by an outlet 
provided. The velocity with which the air is moved is expressed 
by the well-known formula: 

v = ^^gh, (!) 

in which v equals the velocity and h equals the head due to the 
velocity and also to the pressure divided by the density. There- 
fore: 

v = V(2 gp + d). (2) 

The work done in moving this air is equal to the product of the 
velocity of the air in feet per second, the pressure in pounds per 
square foot, and the effective area in square feet over which this 
pressure is exerted. If W represents the work done, p the pres- 
sure in pounds per square foot, a the area in square feet, and v 
the velocity in feet t)er second, then: 

W = pav. (3) 

From (2) we have, by squaring and transposing: 

p = dv* + 2g; (4) 

and substituting its value in (3) we have: 

W = dav z + 2g. (5) 

From this it will be seen that the power required to drive a fan 
varies as the cube of the velocity. In other words, if the velocity 



174 



STEAM POWER PLANTS 



is doubled the power required will be eight-fold; if tripled, 
twenty-seven fold. As the velocity of the air is practically the 
same as the peripheral speed of the fan it will be seen how 
essential it is to use a large fan at its proper speed rather than 
a small fan running at a higher speed than is necessary to ob- 
tain the desired pressure, and thus the desired volume. The 
pressure varies as the square of the speed, as shown in formula 
(4), hence the pressure is quadrupled by doubling the speed. 

Design of Fans. — From the work upon " Mechanical Draft," 
by Mr. Walter B. Snow, published by the B. F. Sturtevant Com- 
pany, the following quotations relating to the design of fans have 
been taken: 

" In the design of a wheel to meet given requirements, it is 
necessary to make its peripheral speed such as to create the de- 




Fig. 53. Cross Section, Power House, Olympia Mills. 



sired pressure, and then so proportion its width as to provide for 
the required air volume. Evidently the velocity and correspond- 
ing pressure may be obtained either with a small wheel running 
at high speed or a large wheel running at low speed. But if the 
diameter of the wheel be taken too small, it may be impossible 
to adopt a width, within reasonable limits, which will permit of 
the passage of the necessary amount of air under the desired 
pressure. Under this condition it will be necessary to run the 



STEAM POWER PLANTS 175 

fan at higher speed in order to obtain the desired volume. But 
this results in raising the pressure above that desired, and in un- 
necessarily increasing the power required. On the other hand, 
if the wheel be made of excessive diameter it will become almost 
impracticable on account of its narrowness. Between these two 
extremes a diameter must be intelligently adopted which will give 
the best proportions. 

" It has been determined experimentally that a peripheral dis- 
charge fan, if enclosed in a case, has the ability, if driven to a 
certain speed, to maintain the pressure corresponding to its tip 
velocity over an effective area which is usually denominated the 
' square inches of blast.' This area is the limit of its capacity 
to maintain the given pressure. If it be increased the pressure 
will be reduced, but if decreased the pressure will remain the 
same. As fan housings are usually constructed, this area is con- 
siderably less than that of either the regular inlet or outlet. 

" The square inches of blast, or, as it may be termed, the 
capacity area of a cased fan, may be approximately expressed by 
the empirical formula: 

Capacity area = DW -s- X. 

In which D = diameter of fan wheel in inches. 

W = width of fan wheel at circumference in inches. 
X = a constant dependent upon the type of fan and 
casing. 

" An approximate value for X for Sturtevant fans for general 
practice is not far from 3, but this is to be used only to determine 
the capacity area over which the given pressure may be main- 
tained. This is not a measure of the area of the casing outlet, 
which is always larger than the square inches of blast. As a 
consequence, the pressure is lower and the volume discharged is 
somewhat greater than would result through an outlet having 
the square inches of blast for its area. But the maximum pres- 
sure may be realized when the sum of resistances is equivalent 
to a reduction of effective outlet area to that of square inches of 
blast. The volume of air which, under the given pressure, will 
flow through the given capacity area, and hence the volumetric 
capacity of the fan under the given conditions, may be determined 
from Table 27. In a similar manner the horse-power may be 
ascertained, the proper efficiency coefficient being applied. 



176 STEAM POWER PLANTS 

11 Both the volume and the power required will evidently in- 
crease with the area of the outlet, being greater with the normal 
outlet than with that representing the capacity area. But this 
increase will not be proportional to the area, for the pressure and 
consequently the velocity will be lower with the larger area. The 
greatest delivery of air and the largest consumption of power will 
occur when the casing is entirely removed and the fan left free to 
discharge entirely around its periphery. 

" If volume alone regardless of pressure is the requisite, the 
larger trie fan the less the power required. There is a strong' 
temptation, however, for a purchaser to buy a smaller fan and 
run it at a higher speed; for he sees only the first cost and does 
not realize the entailed expenditure for extra power. If possible 
a fan should never be made so small that it is necessary to run 
it above the required pressure in order to deliver the necessary 
volume. To double the volume under such circumstances re- 
quires eight times the power; three times the volume demands 
twenty-seven times the power. 

" When a fan is employed for exhausting hot air or gases, the 
speed required to maintain a given pressure difference is evidently 
greater than that necessary when cold air is handled, the differ- 
ence being due to, and inversely proportional to, the absolute 
temperature." 

With forced draft it will be safe to assume that 300 cubic feet 
of air are supplied per pound of coal burned, and with induced 
draft 300 cubic feet supplied but 600 cubic feet exhausted by the 
fan if the gases are to be at a temperature of about 500° F. or 
450 cubic feet exhausted if at 300 degrees temperature, as might 
be expected with economizers. With induced draft the fan has 
to handle hot gases of approximately double the volume that it 
would if the fan was supplying air to the grates. As the gases 
are lighter, however, the power required per cubic foot of gas 
removed is less than it is per cubic foot of air with forced draft. 
Knowing the amount of coal burned under ordinary conditions, 
say four pounds per boiler horse-power per hour, the amount 
of air required per minute can be determined. The draft that 
should be available should be that required to overcome the 
resistance to the passage of air through the grates and of the 
gases through the boiler smoke flue and chimney and through 
an economizer if one is used. The pressures usually required in 




Plate 18. — Cross Section Through the Power Station, Showing the Principal Construction and Equipment Features of the Boiler and Turbine Rooms, 

Metropolitan Electric Company, Reading, Pa. 

WALTER J. JONES, CONSULTING ENGINEER, NEW YORK. 



STEAM POWER PLANTS 



177 



forced draft vary from J to 1 ounce per square inch and in in- 
duced draft from \ to f ounce, depending on the fineness of fuel, 
the readiness with which it burns, the length of flues and number 
of bends in them, etc. A pressure of one ounce per square inch 
is equal to 1.73 inches of water at temperatures of 50° F. 

Tables 27 and 28 are taken from " Mechanical Draft," before 
mentioned. In the former is given the volume of air in cubic 
feet for various pressures which may be discharged in one minute 
through an orifice having an effective area of discharge of one 
square inch, or per square inch of blast. The method of using 
these tables can best be explained, perhaps, by working out a 
typical case. Suppose we are to design an induced-draft fan 
to handle the gases from 1000 horse-power of boilers against a 
pressure of | ounce. At 4 pounds of coal per horse-power per 
hour and 600 cubic feet of gas per pound, 40,000 cubic feet of 
gas would have to be exhausted per minute. Opposite f-ounce 
pressure in Table 27 it will be seen that a fan will supply 31.06 
cubic feet, say 31 cubic feet, per square inch of blast. Dividing 
40,000 by 31 would give 1290 as the number of square inches of 
blast the fan would require. But the square inches of blast equal 
DW -f- 3. In standard fans of the Sturtevant make W is ap- 
proximately equal to D ^ 2.4, therefore: 

Square inches of blast = D 2 -5- 7.2. 

TABLE 27. — VOLUME OF AIR DISCHARGED AND HORSE- 
POWER REQUIRED WHEN AIR UNDER GIVEN PRESSURE IS 
ALLOWED TO ESCAPE INTO THE ATMOSPHERE. 





Volume of air dis- 




Pressure in ounces 
per square inch. 


charged through an ori- 
fice of an effective area 
of discharge of 1 square 
inch (or per square inch 
of blast), cubic feet per 
minute: 


Horse-power required 
to move the given vol- 
umes of air under given 
conditions ol discharge. 


l 

4 


17.95 


0.00122 


3 

8 


21.98 


0.00225 


1 
2 


25.37 


0.00346 


5 

8 


28.36 


0.00483 


3 
4 


31.06 


0.00635 


7 
8 


33.54 


0.00800 


1 


35.85 


0.00978 


11 


38.01 


0.01166 


H 


40.06 


0.01366 


if 


42.0 


0.01577 


l* 


43.86 


0.01794 



178 



STEAM POWER PLANTS 



Substituting 1290 for the square inches of blast we have: 1290 
= D 2 -J- 7.2, from which D equals 96 inches or 8 feet for the diam- 
eter of the fan. 

To determine the velocity at which the fan should be run, 
reference should be made to Table 28. For the column corre- 
sponding to f ounce it will be seen that an 8-foot fan should 
run at 178 revolutions per minute to give the capacity required. 
By increasing the speed at times of overload the pressure and 
volume of gases can be increased. 

In the last column of Table 27 is given the horse-power required 
per square inch of blast to move given quantities of air, under 
different pressures and at a temperature of 50° F. For forced 
draft these quantities can be used directly, but it should be 
remembered that they refer to the theoretical power required 
to move the air and they should be at least doubled to allow for 



TABLE 28. — REVOLUTIONS OF FAN OF GIVEN DIAMETER 
NECESSARY TO MAINTAIN A GIVEN PRESSURE OVER AN 
AREA WHICH IS WITHIN THE CAPACITY OF THE FAN. 



Diam- 
eter of 








Pressure 


in ounces per square inch. 






























wheel, 


i 


i 


3 


l 


5 


3 


7 


1 


14 


H 


in feet. 


8 


4 


8 


2 


8 


4 


8 


3 


194 


274 


336 


388 


433 


475 


513 


548 


581 


612 


3| 


166 


235 


288 


332 


372 


407 


439 


469 


498 


525 


4 


146 


206 


252 


291 


325 


356 


384 


411 


436 


459 


4.1 


129 


183 


224 


258 


289 


316 


342 


365 


387 


408 


5 


116 


164 


202 


232 


260 


285 


308 


329 


349 


367 


5| 


106 


149 


183 


211 


236 


259 


280 


299 


317 


334 


6 


97 


137 


168 


194 


217 


238 


256 


274 


290 


306 


61 


90 


126 


155 


179 


200 


219 


236 


253 


268 


282 


7 


83 


117 


144 


166 


186 


203 


220 


235 


240 


262 


7i 


78 


110 


135 


155 


173 


190 


204 


219 


232 


245 


8 


73 


103 


126 


146 


163 


178 


192 


205 


218 


230 


8| 


69 


97 


119 


137 


153 


167 


181 


194 


205 


216 


9 


65 


92 


112 


129 


144 


158 


171 


183 


194 


204 


9| 


61 


87 


106 


123 


137 


149 


162 


173 


183 


193 


10 


58 


82 


101 


116 


130 


142 


154 


164 


174 


184 


11 


53 


75 


92 


106 


118 


129 


140 


150 


158 


167 


12 


49 


69 


84 


97 


108 


119 


128 


137 


145 


153 


13 


45 


63 


78 


90 


100 


110 


116 


126 


130 


141 


14 


42 


59 


72 


83 


93 


102 


110 


117 


124 


131 


15 


39 


55 


67 


78 


87 


95 


102 


110 


116 


122 



STEAM POWER PLANTS 



179 



the fan and engine friction and the power required to run the fan, 
considering it was moving no air and to overcome the friction 
of the air in the fan casing. 

With induced draft the air is of less density on account of its 
higher temperature, so that less power is required per cubic foot 
of gas moved. If the gases have a temperature of 600 degrees 
the quantities given in the last column of Table 27 can be multi- 
plied by 0.5, and by 0.58 if the temperature is 450 degrees, to 
obtain tfye actual power required to move the air. The engine 
driving the fan should have its cylinders so proportioned that it 
can easily develop power 50 per cent in excess of that calculated. 

Table 29 shows the capacity of the American Blower Com- 
pany's fans used for induced draft, according to its catalogue. 



TABLE 29. — INDUCED DRAFT CAPACITY TABLE FOR FANS. 















O !.• 




-u • 






-*-> 
















'£%* 




osPM 






cs 


9 Sfe 




* 


>> 








3 05o 


&* 


5K 





fa j. 


•43 


a-ir 




is 


.2* 

"<n 


a 


3 

cr 

03 
-2 




_ «"3 

S g)if} 

'egg 

cj S m 
**" "el w 


0" 

a a 




■* u 

o a 
a 

"5 m 


"t« 

oj 


0J <P 

a Q. 

Jj 


1 >> 


t- C J- 


c 




a 




"+j 


P-'-S 


1: » 


<u a 


g^s 


P-i a 


0-0 . 


.9 «? 


*> 2 




2 5 


c3 


<X> 

s 

c3 


3 . 
O wi 





>>5 fa 
.■fa a -3 

'04J cS 




8§ 

-say 




5's b 


C.Q. 


^ fa S 

S 




+3 




g.9 


oJ QJ fa 


Oh" 2 


§ 1 


^ e 

o3,c« 


C3-- 1 *-■ 






m 


5'~ 


12| 


S 

20 


m 


0Q 





w"~ 


&H 


PQ 


O 


.162 


O 


50 


30 


18 


740 


5,030 


116 


580 


2.02 


403 


2,260 


60 


36 


14* 


23 


21* 


615 


6,900 


159 


795 


2.76 


485 


.194 


3,100 


70 


42 


16| 


26 


24i 


530 


9,325 


215 


1,075 


3.72 


563 


.226 


4,200 


80 


48 


17* 


30 


27 


460 


11,300 


261 


1,305 


4.50 


645 


.258 


5,100 


90 


54 


20| 


34 


30f 


410 


15,100 


349 


1,745 


6.03 


728 


.290 


6.800 


100 


60 


23i 


38 


34| 


370 


18,750 


433 


2,165 


7.50 


844 


.322 


8,450 


110 


66 


26 


42 


371 


335 


23,000 


532 


2,660 


9.20 


885 


.354 


10,370 


120 


72 


30* 


46 


41* 


310 


29,250 


677 


3,385 


11.72 


970 


.387 


13,200 


140 


84 


34| 


53 


48 


265 


38,800 


896 


4,480 


15.50 


1132 


.452 


17,450 


160 


96 


38 


60 


54 


230 


49,000 


1130 


5,650 


19.60 


1290 


.516 


22,000 


180 


108 


41* 


68 


60 


205 


59,900 


1385 


6,925 


24.00 


1453 


.581 


27,000 


200 


120 


47 


76 


66 


185 


75,500 


1746 


8,730 


30.25 


1610 


.644 


34,000 


220 


132 


50 


84 


72 


170 


88,600 


2050 


10,250 


35.50 


1775 


.710 


40,000 


240 


144 


54 


92 


78 


155 


104,600 


2420 


12,100 


41.80 


1940 


.775 


47,000 



It is based on a temperature of 550° F. for the gases, and air 
temperature of 62 degrees, on 18 pounds or 234 cubic feet of air 
per pound of coal, and a consumption of 5 pounds of coal per 
boiler horse-power. Mr. F. R. Still, of the American Blower 
Company, recently wrote as follows explaining it: " This table 
gives the diameter of the fan wheel, width at periphery, diameter 
of the inlet, size of the outlet, and the maximum speed necessary 



180 STEAM POWER PLANTS 

to produce a draft of one inch of water, which is about the 
strongest draft that is ordinarily required. The table also gives 
the capacity of the fan per inch of width (of blade) at periphery, 
and the horse-power per inch of width. If it is desired to run the 
fan at a slower speed than is given opposite any of our sizes, 
determine on the speed at which the fan is to run, find the capac- 
ity of same per inch width and divide the required capacity for 
a given horse-power in the plant by this capacity per inch, and 
it will determine how wide the fan should be at the periphery, 
with the increased diameter and the slower speed. The horse- 
power can be determined by multiplying this width by the horse- 
power per inches in width." 



CHAPTER XII. 
CHIMNEYS. 

Size of Chimneys. — There are two factors that affect the 
capacity of a chimney, its cross-sectional area and its height. 
The capacity is proportional to the square root of the height 
of the chimney, and, for a given height, the capacity is directly 
proportional to its cross-sectional area within certain limits. 
Earlier in this book attention has been called to the impor- 
tance of having a strong draft in order that cheap, low-grade 
fuels may be burned successfully, and, also, that there may be 
sufficient reserve capacity in the boilers at times of abnormal 
demands. In this latter respect ample draft is just as good as 
additional boiling-heating surface, and, as a general proposition, 
it costs less. Although an engineer once said that high chimneys 
" are monuments to the folly of their builders," yet this opinion 
should not deter one from building chimneys from 150 to 200 
feet in height, and for very large plants still higher. In cer- 
tain localities where smoke or obnoxious gases are objectionable, 
or where ample draft is required, tall chimneys are necessary. 
Chimneys of the heights mentioned are desirable where high 
rates of combustion are to be employed, and the height of the 
chimney is governed somewhat by the amount of coal that is to 
be burned per square foot of grate in a given time. 

Height of Chimneys. — Mr. J. J. De Kinder, an engineer of 
considerable experience in steam-plant operation, recommends 
the following heights for chimneys with the coals mentioned: 
75 feet for free-burning bituminous coal, 100 feet for slow-burn- 
ing bituminous slack, 115 feet for slow-burning bituminous coal, 
125 feet for anthracite pea coal, 150 feet for anthracite buckwheat 
coal. These recommendations are probably intended for boiler 
plants of moderate size only. As a matter of fact the height is 
governed by the draft required to burn the kind of coal that is 
to be used as shown in the following section. 

181 



182 



STEAM POWER PLANTS 



Draft. — In Chapter II it was shown how a boiler plant should 
be provided with a grate large enough so that with a given draft 
sufficient coal could be burned to generate the steam required. 
Now the amount of draft theoretically available depends upon 
the height of the chimney, if a chimney is used, and the draft 
available for promoting combustion is the theoretical draft less 
the draft used up by the friction of the gases in passing through 
the boiler, the smoke flue, and the chimney. It is proposed in 
this chapter to give some idea of the friction due to the passage 
of air through fuels of different kinds at different rates of com- 
bustion, and the friction in boilers, smoke flues, and chimneys, so 
that it is possible to obtain a proper relation between grate area, 
flue area, and stack dimension. 

Table 30 gives the theoretical draft in inches of water that will 
be obtained from a chimney 100 feet high for various outside 
temperatures and for various temperatures of waste gases, the 
table being based upon a barometric pressure of 30 inches. 

TABLE 30. — THEORETICAL DRAFTS IN CHIMNEYS. 



Chimney temperature. 


Temperature externa! 


air. 


30° 


60° 


90° 


300° 

400° 

500° 


.511 
.632 
.730 


.420 
.541 
.639 


.340 
.461 
.559 



Gas temperatures of from 400 to 500 degrees can be assumed 
for most power boilers if run at their usual rating, and the outside 
temperatures can be taken at 90 degrees if the full load obtains 
in the summer time. The theoretical draft varies directly as 
the height of chimney, hence the draft for other heights can be 
obtained by direct proportion. 

The draft required to move the air through the fires varies 
with the kind of coal, and with the thickness of the bed of fuel 
on the grate. The Stirling boiler catalogue gives data, from 
which Table 31 has been prepared, showing the draft in inches 
of water required to burn different kinds of coal at the various 
rates of combustion under average conditions. 



STEAM POWER PLANTS 



183 



TABLE 31.— DRAFT IN INCHES OF WATER TO BURN DIF- 
FERENT COALS. 



Pounds coal per square foot grate per hour. 



No. 3, buckwheat anthracite 
No. 1, buckwheat anthracite 

Anthracite pea 

Run of mine semibituminous. 

Bituminous slack 

Run of mine bituminous 



10 



.40 
.23 
.16 
.08 
.07 
.05 



15 



.74 
43 
.30 
.13 
.11 
.08 



20 



1.25 
.68 
.45 
.20 
.16 
.10 



30 



37 

27 
17 



40 



.62 
.42 

.27 



The friction of the gas passages in a Babcock and Wilcox 
boiler and a Stirling boiler when run at rating is about 0.2 inch 
of water, and at 50 per cent overload about 0.40 inch. The 
friction of a horizontal tubular boiler is about the same. 

A common method of proportioning flues is to allow 35 square 
feet of sectional area per thousand horse-power in boilers. This 
is hardly a correct method as the frictional loss does not vary 
with the cross section. Table 32 has been prepared giving the 
sectional area of flue required for different boiler capacities for 

TABLE 32. — FRICTIONAL LOSS IN SQUARE IRON FLUES IN 
INCHES OF WATER PER 100 FEET OF LENGTH. 



Horse-power. 


100 


200 


300 


400 


500 


600 


800 


1000 


1500 


2000 


2500 


Area flue, sq. ft. for 
























.05 in. frictional loss 


3.9 


6.6 


9.0 


11.2 


13.5 


15.4 


19.5 


22.8 


31.0 


38 


46 


Friction sharp bend. . 


.18 


.245 


.305 


.340 


.375 


.410 


.460 


.510 


.620 


.700 


.76 


Friction easy bend . . . 


.080 


.110 


.130 


.148 


.165 


.180 


.207 


.225 


.275 


.310 


.343 


Area flue, sq. ft. for 
























. 03 in. frictional loss 


4.8 


7.9 


10.1 


13.8 


16.2 


18.5 


24.5 


27.0 


36.7 


46.0 


54.0 


Friction sharp bend. . 


.123 


.170 


.210 


.235 


.265 


.290 


.330 


.362 


.430 


.490 


.542 


Friction easy bend. . . 


.054 


.077 


.092 


.105 


.113 


.128 


.153 


.160 


.197 


.222 


.240 


Area flue, sq. ft. for 
























.01 in. frictional loss 


7.4 


12.5 


17.0 


21.5 


25.0 


30.0 


36.5 


42.8 


59.0 


73.0 


87.5 


Friction sharp bend. . 


.053 


.070 


.087 


.104 


.110 


.125 


.135 


.148 


.180 


.205 


.228 


Friction easy bend . . 


.023 


.032 


.039 


.045 


.048 


.053 


.060 


.065 .079 

1 


.091 


.100 



frictional losses of 0.05 inch, 0.03 inch, and 0.01 inch of water 
for a flue 100 feet in length. The frictional loss in bends of a 
flue of the same sectional area is also given, the first case being 
for an abrupt right-angle bend, and the second case for an easy 
bend with the inside radius of the bend equal to the width of 
the flue. 

The friction is based upon 500 cubic feet of gas per pound of 
coal, 4 pounds of coal per boiler horse-power, and the friction 
is given for iron flues of square section. For brick flues the 



184 STEAM POWER PLANTS 

friction will be one-third greater, and for flues that are not square 
with sides as 1 : 2 the friction will be 7 per cent greater than that 
given. For round flues it will be 87 per cent of that given. 

From the table it will be seen that a straight flue 100 feet 
long for 2500 horse-power of 46 square feet sectional area will 
have a frictional loss of 0.05 inch of water. A sharp bend in 
this flue will cause an additional friction of 0.76 inch of water 
and the sum of these will be too great for most cases, hence a flue 
of greater sectional area will be required. 

Calculation has been made of the friction of gases in chimneys 
of the sizes given in the Kent table and the result is given in 
Table 33. The friction of each based upon 4 pounds of coal 
per horse-power hour and 500 cubic feet of gas per pound of coal, 
for both iron and brick stacks, is given. All of the data upon 
friction was obtained from a friction loss chart presented by 
Mr. Konrad Meier in his book on the " Mechanics of Heating 
and Ventilation," and based upon the following formula repre- 
senting the frictional loss: 

yi.9 /A1.18 . 

2<7 W " 

The data upon friction may be used as follows: Suppose that 
it is desired to find the size of chimney and flue for a maximum 
capacity of 1000 boiler horse-power based upon the use of four 
pounds of No. 1 buckwheat coal per horse and that it is desired 
to burn the coal at the rate of 15 pounds per square foot of grate 
per hour, requiring a difference in pressure between the ashpit 
and furnace of 0.43 inch of water, the chimney and flue to be 
iron. It is further assumed that the load on the plant is fairly 
constant, that the boilers are to be run at their normal rating of 
1000 horse-power, and that the flue-gas temperature will be 500 
degrees and the outside-air temperature 60 degrees. The con- 
ditions are such that there will be a sharp right-angle bend in the 
flue as the gases enter the chimney, and the gases will have to 
make a similar turn in entering the flue from each boiler. From 
Table 31 it will be seen that the frictional loss of the gases passing 
through the fires will be 0.043 inch of water, and as this is quite 
high a tall chimney will be required, hence low losses in the flue are 
desirable. A flue of 42.8 square-feet area and 100 feet long and 
a chimney 60 inches in diameter and 200 feet high which is rated 
according to Table 33 as being of 1000 horse-power will be tried. 



P f = 0.075 X 0.00624 ^-l[- 



ye Dio *?SOQ' 
RoomF/oor 




'unnel 



Company, Chicago, III. 




p>- -j i , I ] ! 'Mofwe// Pump | I " InjectionTunnel 



Plate 19. — Cross Section of Quarry Street Station, Commonwealth Edison Company, Chicago, III. 

SARGENT AND LONDV, CONSULTING ENGINEERS. 



STEAM POWER PLANTS 



185 



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186 STEAM POWER PLANTS 

Before deciding upon the size the data given should be used to 
see if the draft from such a chimney will be sufficient. The 
various frictional losses in inches of water will be approximately 
as follows: 

Friction of fuel on grates . 430 

Friction of boilers 0.200 

Friction of square flue 0.010 

Friction of two sharp bends (2 by 0.148) 0.296 

Friction of chimney . 097 

1.033 

Now the theoretical draft for a 100-foot chimney with flue 
gas at 500 degrees and an outside temperature of 60 degrees is 
0.639 inch of water, and for a chimney 200 feet high 1.278 inches, 
hence the chimney ought to be amply large enough to do this 
work. If the theoretical draft had not been sufficient the grate 
area might be increased to operate at a lower rate of combustion, 
which would reduce the frictional loss through the fires, or the 
chimney could be increased in height to increase the draft. The 
former is the cheaper method to pursue. While increasing the 
height of the chimney increases the theoretical draft directly 
as the height is increased, the friction of the chimney is increased 
at the same rate, but as the chimney friction, in this case 0.097 
inch, is a small part of the total, this method of increasing the 
draft may be used. 

Capacity of Chimneys. — Most chimney formulas are based 
on coal consumption but do not take into account the fact that 
the amount of gases given off by different coals varies. Col. E. 
D. Meier has called attention to this, and by calculating the 
volume of gases from their composition finds that the relative 
areas for chimneys for certain much-used coals should be as 
follows: Anthracite 100, New River (Va. semi-bit.) 93, Youghio- 
gheny (Penn. bit.) 102, Mt. Olive (111. bit.) 128, Collinsville 
(111. bit.) 138. 

Three well-known chimney formulas are those of Kent, Gale, 
and Christie. In the first 

K.P. = 3 : 33EVH, 

in which H is the height in feet and E is the effective area, the 
actual area being determined by increasing the diameter of the 
chimney if it be round or the side of the chimney if it be square 



STEAM POWER PLANTS 



187 







E/. re- 



sect ion at Elev.200'0* 



Section at Elev43'6 



Section at Clev I5'0" 



Fig. 54. Chimney, Metropolitan Street Railway Co., New York. 



188 STEAM POWER PLANTS 

by four inches to allow for the lining of the chimney by a layer 
of gas that is assumed to have n'o velocity. E is approximately 
equal to (A — 0.6 VA) for round chimneys and to A — f VA 
for square chimneys. As this formula is based upon the burning 
of five pounds of coal per horse-power 

c = iq.qeVh, 

where C equals the number of pounds of coal burned per hour. 
The Kent formula assumes that the height and area are inter- 
dependent, and it only holds within certain limits. Kent's table 
of chimney capacities is given in Table 33 with the frictional loss 
in inches of water. 

Gale's formula may be expressed in the form: 

A n,^f A rr 180 /tf\ 2 

A = 0.07 C and H = — - f ^ j , 

in which t is the temperature of the chimney gases and G the 
grate area in square feet. Col. E. D. Meier, who has a great 
deal of experience with western coals, states that this formula 
gives rather too large results and recommends that: 

»■'-?©'■ 

and that after the height is found by this formula the area be 
obtained by the one proposed by Mr. Kent. 

Mr. George A. Orrok in " Power " states that the constant 
in the general chimney formula, for which Kent gives the value 
of 16.66, varies greatly in the formulas of different authorities, 
and Mr. Orrok recommends that a value of 12 be given it for 
brick-lined stacks, but that in case of an unlined steel stack the 
value of this constant may be increased to 14 or 15 and for small 
stacks 16 may be used. 

Mr. W. W. Christie in his book on " Chimney Design " gives 

the chimney formula : Horse-power = 3.24 A VH, it being assumed 
that four pounds of coal are burned per horse-power, A being 
the area of the flue and H the height, both in feet. If C is the 
coal burned per hour C = 12.96 A v#. 

Thickness of Chimney Walls. — In designing a chimney of a 
given height and inside diameter it is necessary to determine the 



STEAM POWER PLANTS 189 

thickness of the walls required to provide sufficient weight to 
prevent its being overthrown by the wind. It is customary to 
step out the inner walls at different levels so as to divide the shell 
into a series of sections, each of a uniform thickness which is less 
than that of the section immediately below it. As the walls have 
a slight batter inside and outside, the diameters at the top and 
bottom and the thickness and heights of the different sections of 
the shell have to be determined. To simplify the problem it is 
proposed to give a method of designing a chimney with straight 
inner and outer walls of the proper batter. From this a chimney 
of approximately equivalent weight but made up of several 
sections each of uniform thickness can be designed. 

It is usually customary to make the weight of a chimney such 
that it will bear a certain relation to the wind pressure, a rule 
commonly used requiring that the prolongation of the resultant 
of the total wind pressure acting through the center pressure 
and the weight of the chimney intersect a horizontal plane 
through the chimney base at a point not more remote from the 
axis of the chimney than a distance equal to D b 4- 6 where D b 
represents the outside diameter at the base, or at the elevation at 
which the calculation for stability is made. If the chimney be 
round, square, or octagonal, the diameters referred to are those 
of the inscribed circles. To illustrate, if, in Fig. 56, CD rep- 
resents the wind pressure considered to be acting through the 
center of pressure C, and CE represents the weight of the chim- 
ney, and the prolongation of their resultant CF intersects the 
base A B at a point G distant from H by a distance less than 
D b -r- 6, then the conditions as to stability are fulfilled. In 
Fig. 56, C is the center of pressure; CD represents the total wind 
pressure P; CE the weight W; and CH equals h, the height in 
feet of the center of pressure above the base A B. Expressed 
algebraically the formula is: 

£--*-■. ■ (1) 

P D b + 6 K } 

The value of W can be found from the volume of the chimney, 
assuming that one cubic foot of brick masonry weighs 115 pounds. 
Then W = 115 V. Therefore: 

W = 115 Hit ( W + D * + DhDt) ~ W + dt * + dbdt) ) (2) 



Cast Iron Caps Bedded 
in Portland Cement 




Fig. 55. Brick Chimney designed by Lockwood, Greene and Co. 



190 



STEAM POWER PLANTS 191 

Throughout this discussion the terms used have the following 
significance : 

H = height of chimney above base in feet. 
h = height of center of pressure above base in feet. 
D t — outside diameter top in feet. 
d t = inside diameter top in feet. 
D b = outside diameter bottom in feet 
d b = inside diameter bottom in feet. 
P = equivalent total wind pressure. 

Now if the value of W in equation (2) be substituted for W in 
equation (1) then: 

n k tt /(Db 2 + D t 2 + DbDt) ~ W + d? + dtd t ) \ 6/iP 

U57rH { 12 T^T (3) 

There is but one factor in this equation, d b , whose numerical 
value is not known either from data assumed at the outset or 
from its relation to known quantities in the equation. This 
being the case the equation can be solved for the value of d b 
and its numerical value obtained. One would then have all the 
dimensions of a chimney with straight walls of a height and in- 
side diameter necessary, and which would satisfy conditions of 
stability. 

The inside diameter of the chimney at the top and the height 
must be assumed. From the former dimension the outside 
diameter at the top and the outside diameter at the bottom can 
be found readily by two empirical rules. The first of these is 
Professor Lang's rule, given in his paper on the " Construction 
and Dimensions of Chimneys for Boiler Plants," of which a 
translation was printed in The Engineering Record of July 20 
and 27, 1901. It is to the effect that the thickness in feet of a 
chimney at the top, t, neglecting the ornamentation, should be: 

t = 0.328 + 0.05 d t + 0.0005 H ; 
therefore : 

D t = d t + 2 1 = 0.656 + 1.1 d t + 0.001 H. (4) 

The minimum value of t should be 0.58 foot for radial brick 
and 0.7 foot for common brick. As the thickness must be over 
a brick's length and as it cannot increase by less than half a 
brick's length, the value of t must be 0.7, 1.08 feet, etc. Few 



192 



STEAM POWER PLANTS 



Or 



'IT 



Ft 



\S H 



3 



k 



,B 



\H 



ZA_J 



V 



* 



T 



Mi 



Fig. 56. 



Fig. 57. 



k- 



h\ 



Fig. 58. 



_4 



chimneys built of common brick have a value for t greater 
than 1.08 feet. The outside diameter at the bottom, or D b , 
can be obtained from the outside diameter at the top by a rule 
which assumes a batter for the outside wall of 1 : 30 to 1 : 36 on 
a side. Assuming it to be 1 : 32 then: 



mpk 



L 



'M Ifl 




ircllWBBiiiiwmiJWinjTom 






•>•'- 



Hf1OTtii]W : m 



Plate 20. — Cross-Section Elevation of Main Power House op the New Orleans Railway and Lighting Company. 

SANDERSON AND PORTER, ENGINEERS. 



STEAM POWER PLANTS 193 

substituting the value of D t from equation (4) then: 
D b = 0.656 + 1.1 d t + 0.001 H + j| = 0.656 + l.ld t + 0.063 ff. 

The value for P, the total wind pressure in equation (3), is 
found by multiplying the assumed wind pressure of 50 pounds 
per square foot by the equivalent of the vertical cross section 
of the chimney through the axis, in square feet. With a square 
chimney this plane is taken parallel to two opposite sides. For 
square chimneys P has a value equal to their cross section in 
square feet, for round chimneys 0.50 times this area, and for 
octagonal ones 0.71 times this area. 

The numerical values of H, D b , D t , d t , P, and H found in the 
manner indicated are substituted in the above equation, which 
then can be solved for the value of d h . This determined we have 
all the dimensions of the straight-walled chimney of the height 
and inside diameter required for the capacity, and which fulfills 
the conditions as to stability. As has been said, the interior of 
a chimney is seldom constructed with a straight batter, but in a 
series of steps each section from the top downward increasing 
in thickness by half a brick's length. Each step should then be 
of a thickness in inches that is divisible by 4J, this being the 
width of a brick and the necessary mortar. From the top down, 
therefore, the thicknesses of the different sections should be 
8J, 13, 17J, 22, 26J, etc., inches. Should the calculations for 
the thickness of the wall at the bottom call for a thickness inter- 
mediate between two of these thicknesses, the greater one can 
be selected as the thickness of the bottom section. Should such 
calculation show that the thickness at the bottom should be 
22 inches, the chimney can be divided into four sections of equal 
height, 8J, 13, 17J, and 22 inches thick. Radial brick for chim- 
neys are made in several sizes so that the thickness, when they 
are used, increases by about two inches at the offsets. 

After the thickness of walls of the different sections and their 
heights are determined, the calculation for stability must be 
made at the base of' each section, paying no attention to that 
below. For instance in Fig. 57, the stability of the part ABJI 
should be calculated considering IJ as the base, also ABHG 
considering GH the base, etc., each time locating the center of 
pressure for the part under consideration. 



194 STEAM POWER PLANTS 

Another operation yet remains, and that is to find the pressure 
imposed upon the brickwork by its own weight. Calculation 
must be made as to the pressure per square inch at the base, 
and at each level where the shell changes in thickness, that is, 
at the bottom of each section. According to Professor Lang, the 
pressure in pounds per square inch should nowhere exceed that 
given by the formula P = 71 + 0.65 L, where L denotes the 
distance in feet from the top of the chimney to the point in 
question. Should the pressure exceed that given by the formula 
the walls of the chimney should be made thicker. The function 
of the chimney height is introduced in the formula to allow 
a greater pressure in high chimneys, which are erected less 
quickly than shorter ones, the mortar therefore having more 
time to harden. 

Chimney Linings, etc. — Chimneys of common brick built 
in the United States are usually provided with an inner core or 
lining to protect the outer shell from the heat. Sometimes this 
core is carried up for half the height of the chimney, but more 
usually to the top. Care should be taken that it is built inde- 
pendently of the outer shell as the greater expansion of the core 
would injure the shell. With radial brick chimneys the inner 
core is not so common as the bricks are more carefully burned 
and selected than is the custom with common brick and are not 
so easily affected by heat. Any chimney likely to contain gases 
at a higher temperature than 600° F. should be lined with fire 
brick set in fire clay or lime mortar, preferably the former. 
Sometimes the fire-brick lining extends from the bottom to one- 
third or one-half of the height. The core can be divided into 
sections, each about 40 to 50 feet high, and 4, 8|, 13, 17J, and 
21 inches in thickness from the top down. If the chimney is of 
fairly large diameter the 4-inch section should not be over 25 or 
30 feet. In the largest chimneys 8 inches is the minimum thick- 
ness of the core. It usually has a uniform inside diameter so 
that changes in thickness are secured by offsets on the outside. 
With the batter for the outer surface of the outside shell recom- 
mended in an earlier paragraph there is likely to be sufficient 
distance between the offsets of the core and those of the outer 
shell to provide proper clearance. When the chimney is drawn 
on paper this can be determined. Steel chimneys should also 
be lined to prevent loss of heat and also air leakage, which will 



STEAM POWER PLANTS 



195 



*\0O"* 



^ 



Scale. 

O 7 10' 20' 30' 40' 

1 ' t ' ' ■ ' 




Section A- B. 



B 



— D 



Common 
brick 

Fire, Brick. 



Al 




Section OD. 



Fig. 59. Custodis Radial Brick Chimney for Orford Copper Co. 



196 



STEAM POWER PLANTS 




ELEVATION 

Fig. 60. Chimney, Laidlaw-Dunn-Gordon Co., Cincinnati, Ohio. 






STEAM POWER PLANTS 197 

occur unless the joints are carefully calked, a provision that is 
frequently overlooked. 

In constructing the opening for smoke flues at the base of the 
chimney care should be taken that it is not weakened at that 
point. The top of the opening should be arched over or spanned 
with heavy steel beams built in the masonry. Should the chim- 
ney have an inner core the smoke flue should, of course, be 
continuous through both shells. Ladders for reaching the top 
of a chimney are usually located on the inside of brick chimneys 
and more frequently on the outside of steel ones. If the latter, 
the continuous hand rails at the sides should be so designed as 
to allow for the possibility of a difference in expansion between 
the ladder and the chimney. The tops of brick chimneys should 
be covered with a cast-iron cap held in place by anchor bolts, 
and lightning rods metallically connected to the ground should 
also be provided. 

Materials. — Masonry chimneys are usually built of brick, 
but recently concrete chimneys reenforced with steel, as in the 
Ransome chimney, shown in Fig. 61, have been used with 
success. For brick chimneys hard burned brick of high specific 
gravity should be used. A special brick for chimney building 
used to a large extent in Europe and to a rapidly increasing 
extent in the United States is the radial brick for round chim- 
neys, with its inner and outer surface curved to conform to the 
curvature of the chimney. Several holes running through the 
brick aid in the burning and also serve to secure it in place more 
strongly as the mortar works into them when the brick is laid. 
The radial brick that have been used to a considerable extent 
by the Custodis and Heinicke companies in Germany are much 
stronger and more durable than common brick. Another fea- 
ture in their favor is that they are considerably larger than com- 
mon brick and less labor is required in laying them. 

Masonry Chimney Foundations. — These should be of such 
an area that the load per square foot does not exceed one ton 
per square foot on soft clay; two tons per square foot on stiff 
clay, compact sand, loam, etc. These loads are exceeded in 
buildings but they should not be in chimneys unless solid rock 
underlies the foundation. The rock should be dressed off into 
steps with vertical sides so there will be no tendency to slide. 
With very large masonry chimneys, and in fact with chimneys 



/i'lfcrf in 
tach Core. 



^ Rings.- 

^'Twisted 
Steel Bars 
iOVLong; 



WTwisted 
Steel Bars 
I0'0'> Long. 

k' Rings. 






Section E _ F. 



'js" Rings- 



Section I- J 




^ Twisted Steel 
BarsZ'0"Long.I8"0.C 
V£ftj,W-Bars Wti'Long. 



Section C-D. 




Vertical Bars ^'Twisted 
Steel. 

Vertical Bars \° 
Twisted Steel. 

Rings ofV'Twistzd 
Steel Bars. l'6"0.C. 



Section A-B. 



Section G-H. 



ZRinqsMTwistecjA\ 
Steel S 1 



o>?, 



Filled with 
large Stones. 



Rings 
Wars. 



Half Section. 



Fig. 61. 



\ H Twisted Steel Bars. 
Half Elevation. 




k7'0" 
Twist e 



Half Plan of Footing 
showing Piling. 



■feel Bars. 
Half Plan of Footing 
showing Steel. 



Ransome Concrete Steel Chimney, Central Lard Co., 
Hoboken, N. J. 



198 



STEAM POWER PLANTS 199 

of moderate size in soil of low-bearing power, pile foundations 
are frequently resorted to, the piles being driven on about 2\- 
foot centers and cut off below the level of surface water; they 
support a concrete bed two or more feet in thickness into which 
their tops extend. Concrete or brick foundations laid in cement 
mortar should be laid several weeks before the chimney is con- 
structed in order that the cement should set properly. The 
sides of the foundations which are usually in the form of a trun- 
cated pyramid should have an inclination of at least 60 degrees 
to the horizontal. The depth of the foundation should be such 
as to properly distribute the load. 

Steel Chimneys. — Chimneys built of sheet steel are common, 
particularly in Pennsylvania and the middle West. They may 
be either self-supporting or held in position by means of guy 
ropes. To save expense, it is not unusual for a considerable 
number of small guyed chimneys to be used in place of one large 
chimney. Steel chimneys are said to cost less than those built 
of brick but the market price of steel affects their relative cost 
considerably. Any steel chimney should be carefully calked at 
the joints and the vertical lap joints scarfed at the girth seams. 
The leakage of air that would otherwise occur and which unfor- 
tunately does occur in many cheaply built steel chimneys very 
greatly affects the draft. Self-supporting steel chimneys rest 
usually on cast-iron base plates sometimes cast in sections and 
bolted together if the chimney be large enough to make this de- 
sirable. The base plate is held down by foundation bolts built 
in a brick or concrete foundation sufficiently heavy to prevent 
the chimney from overturning. The lower courses of a self- 
supporting stack are usually flared out at the base of the chimney 
in a conical or bell shape, to give stiffness to it, the height of this 
cone or bell being from 1 \ to 2 times the diameter of the chimney 
above the bell and of a diameter at the base equal to the height 
of the bell. 

A formula for determining the thickness of shell that is used 

by a firm which has built a large number of large self-supporting 

steel chimneys is as follows: 

moment in inch pounds , ,. . . . 

_ „ . r ^ = stress per lineal inch. 

U.7o4oi^ z 

This assumes that the moment of the total wind pressure in 
pounds multiplied by the distance in inches of the section under 



200 STEAM POWER PLANTS 

consideration from the center of pressure, divided by the diam- 
eter of the chimney in inches squared multiplied by 0.7854, is 
equal to the maximum stress per lineal inch in the shell. The 
total wind pressure is based on an assumed pressure of 25 pounds 
per square foot of projected area. A safe working stress is 
10,000 pounds per square inch and this should be reduced by the 
efficiency of the riveted joint. If the efficiency of the riveted 
joint is 60 per cent, then 6000 pounds per lineal inch would be a 
safe working strength and the ratio of the stress per lineal inch, 
as found by the equation, to 6000 would be the thickness in inches 
of the shell required at the section under consideration. Calcu- 
lation for the thickness of the shell should be made at the base 
of the stack, the top of the bell, and several points between it 
and the top. The greatest strain occurs at the top of the bell. 
On account of deterioration that is apt to occur in the steel, 
it is undesirable to use shells less than f to \ inch in thickness, 
depending upon the size of the chimney. This is particularly 
true near the top where the greatest corrosion is apt to occur, 
owing to the effect of the smoke that usually clings to the lee- 
side of a chimney. 

For about one-fifth or one-quarter the height of a self-support- 
ing chimney it is desirable that the girth seams be double-riveted. 
The lower edge of any sheet usually overlaps the upper edge of 
the sheet beneath it. For the sake of the greater stiffness, the 
vertical seams at the bell should also be double-riveted. 

Foundations for Self-Supporting Steel Chimneys. — The foun- 
dations for self-supporting steel chimneys should have such a 
base that the load caused by the weight of the chimney and base 
and by the wind pressure on the leeward half of the base does not 
exceed the requirements of safety. The weight of the lining, 
if there be any, is to be neglected. The foundation must have 
sufficient mass so that the moment of the wind pressure by the 
height of the foundation plus half the height of the steel shell 
shall be equal to the weight of the shell plus the weight of the 
foundation multiplied by one-third the length of the base of the 
foundation. 

If P is the total wind pressure, W s the weight of the stack, 
W f the weight of the foundation, all in pounds, then in Fig. 58 
the conditions as to stability are fulfilled when 




Plate 21.— Sectional Elevation of Consumers Power Company, Stillwate* (Mlnn.) Turbine Generating Station. 

H. M. BYLLESBY AND COMPANY. ENGINEERS. •- 



STEAM POWER PLANTS 



201 



mchor Plate 




<■- -II O- )| 



& ! 
I 




V%3 *5^ 

i COPING PLATES 



i 8 





i >-//&": 



to n z? 



i/?'/^ 



t$ 



,ffVhsklb\ 



^Casf Base Plate 



ELECTION OF SEGMENT ON LINE X"X. 



Fig. 62. Steel Chimney at Wilmerding, Pa. (Built by the Riter-Coaley 

Manufacturing Co.) 



202 STEAM POWER PLANTS 

The wind pressure can be obtained by calculation and the 
height of the foundation can be taken at from one-eighth to one- 
tenth the total height of the chimney. With these data and the 
weight of the stack being known, the weight of the foundation 
can be calculated. As concrete weighs about 140 pounds per 
cubic foot, the volume of the foundation can be determined and 
from this the area of the top and bottom. The slope of the sides 
can be to 1 to 3. Should the wind pressure be found to cause 
too great a load along the leeward edge of the foundations, a 
foundation of less depth which would insure one of greater area 
can be assumed. 

Information as to the size of smoke flues is given in the article 
on " Draft " in this chapter. Material for flues may be of 
masonry, preferably brick, of black iron varying from No. 10 
for very small boilers up to, say, f inch thick for large plants. 
For substantial work with a smoke flue 4 feet by 5 feet in section 
Te-inch iron may be used with 2\ by 2j-inch angles at all corners, 
and at circumferential joints with stiffening angles of the same 
size on top placed about four feet apart. Expansion joints of 
the sleeve type should be placed in long flues when expansion 
might be troublesome. The main damper should have outside 
lever for damper connection with checks limiting the swing 
through an angle of 90 degrees. Clean-out doors should have 
bar iron frames, latch, and hinges. Dampers in branch con- 
nections from main flue to each boiler should have some form of 
locking device so they may be fixed in any desired position. 



CHAPTER XIII. 

COAL HANDLING, WATER SUPPLY, AND 
PURIFICATION. 

Coal-handling Machinery. — One of the most important fac- 
tors governing the selection of a location for a steam power 
plant is the cost at which coal, assuming this fuel is to be used, 
can be transported to the boiler plant and the cost of the disposal 
of the ashes. Because coal can frequently be conveyed more 
cheaply by water than by rail large power plants are located 
upon navigable waterways, if it is convenient to do so, and if 
not, the site should be near a railroad if possible, so that coal 
can be delivered at the minimum expense. Of course the ex- 
penditure to which one should go in providing means for han- 
dling coal and ashes depends entirely upon the amount to be 
burned, as the cost of handling coal may be so small compared 
to other expenses as to be of secondary consideration. Even 
in the smallest plants, however, thought should be given the 
matter of coal delivery. If coal-handling machinery is not used 
it is a convenient arrangement to have coal pockets or coal bunk- 
ers located next to the wall of a boiler room so that coal will 
fall from them by gravity to the floor in front of the furnace 
doors. If possible, arrangements should be made for delivering 
the coal to the bunkers directly from the coal cars, whether they 
be steam-railroad coal cars or small dumping cars of an auto- 
matic railway run from some near-by wharf. As plants increase 
in size greater expense for coal-handling apparatus is warranted. 
Means should be provided for storing coal and the amount of 
storage space required depends, in a measure, upon the effect 
of an enforced shutdown. For an electric-lighting or railway 
power station, or for power and heat for hospital buildings or 
public institutions, large storage capacity is imperative, par- 
ticularly in localities where there is likely to be an interruption 
in the supply of fuel. 

203 



204 



STEAM POWER PLANTS 



With plants as small as 500 or 600 horse-power in boilers, 
coal-handling machinery is frequently installed. It usually con- 
sists of a receiving hopper, into which the coal is delivered, 
feeding to an endless chain of buckets which elevates and con- 
veys the coal to bunkers placed over the boilers; spouts lead 
from the bunkers to the floor near the furnace doors of the 
boilers if they are hand-fired or to mechanical stokers if the latter 




Fig. 63. Cross Section, Power House Central Lard Co. 

v 

are provided. Frequently the conveyor is arranged to pass 

beneath ash hoppers under the boiler grates so that when not 
handling coal it can be used to elevate the ashes into a storage 
bin, from which they can be removed by carts or otherwise. 
When coal is delivered by boat to a plant, particularly in large 
stations, it is frequently elevated by a self-filling bucket and 
raised by a boom to an elevated coal hopper in a tower on the 
wharf; the coal falls through a crusher to reduce it in size and 
then passes through automatic weighing scales to the con- 
veyors which deliver it into bunkers over the boilers. Some- 
times large storage bunkers are built outside of a power house, 
these being filled by conveyors, while a second conveyor extends 
from the storage bunker to a smaller bunker over the boilers. 
Some idea of the varied manner in which coal-handling machinery 
for power houses may be applied can be had by examining the 
illustrated catalogues of makers of this class of machinery. 



STEAM POWER PLANTS 



205 



Cost of Coal Handling by Machinery. — For the purpose of 
showing the relative cost of hand firing and a modern coal-han- 
dling equipment combined with mechanical stokers in large 
plants, some pertinent figures have been obtained through the 
courtesy of a well-known electrical-supply company owning a 
plant, containing about 7500 horse-power in boilers, which was 
operated for some time after construction without any kind of 
coal-handling machinery other than small hand cars which were 
loaded by hand from railway cars outside of the building and 
then hauled up a slight incline to the boiler house, so that the 
fuel could be dumped in front of the furnaces. The cost is given 
for two months, a year apart; during the first month, the plant 
was run without and during the second month with coal-handling 
machinery and mechanical stokers. The coal-handling plant 
consisted of a McCaslin conveyor so arranged that the coal was 
only handled by hand in shoveling it out of railway cars onto 
the conveying system: 



May, 1900. 


Wages. 


Tons of 

coal 
burned. 


Cost per 
ton. 


16 firemen and one helper 

11 coal and ash men. Ash removing by 
contract 


$981.80 
634.66 

287.75 
654.50 


4292 
6975 


10.229 
0.1478 

0.041 
0.0938 


May, 1901. 
3 firemen and 2 helpers 


11 coal and ash men, 2 conveyor men 





The saving in wages of firemen and helpers amounts to 18.8 
cents per ton, which is 82.1 per cent or $1311.30 per month. 
The saving on coal and ash handling is 5.4 cents per ton, which is 
41.4 per cent or $376.55 per month, or a total saving of $1687.85 
per month or over $20,000 per year. Were it not for the fact 
that, owing to peculiar local conditions, the coal has to be shoveled 
from the coal cars onto the conveyor system the cost of labor 
might be still further reduced. 

Cost of Boiler-room Labor. — This matter is of importance in 
deciding upon methods of handling coal in steam power plants, 
and some valuable information in this connection was contained 
in a report by Mr. R. S. Hale to the Steam Users' Association, 
whose members represented nearly 400 mill owners, largely in 
New England and the Middle States. Judging from the replies 



206 



STEAM POWER PLANTS 



received from members owning a total of about 600 boilers, it 
costs to move coal by hand (wheelbarrow) about 1.6 cents per 
ton per yard up to distances of five yards, then about 0.1 cent 



A 

1 




per ton per yard for each additional yard. Mr. Hale found that 
one man, besides a night man, can run an engine and fire up to 
about 10 tons of coal per week. One man, besides an engineer 



STEAM POWER PLANTS 



207 



and night man, can fire up to about 35 tons per week. Two 
men, besides an engineer and night man, can fire up to about 
80 tons per week. These figures assume that the night man 
does all he can of the banking, cleaning, and starting. The 



I 




figures are for average conditions. If the conditions are excep- 
tional, as, for instance, where there is a very long wheeling dis- 
tance or a very variable load, proper allowance should be made. 
Mr. Hale states in the report that mechanical stokers save from 



208 STEAM POWER PLANTS 

30 to 40 per cent of the labor in plants burning from 50 to 150 
tons per week and save no labor in small plants. Boiler attend- 
ants are paid about $1.50 per day, working from 10 to 12 hours. 
The average cost of firing coal, according to the report, was 
48 cents per ton, the maximum 71 cents and the minimum 
26 cents. 

Mechanical Stokers. — In the chapter on mechanical draft it 
was explained that perfect combustion required just the proper 
amount of air to be supplied the furnace of a steam boiler. That 
requirement is difficult to fulfill where fuel is fired by hand. If 
the bed of fuel is too thin there will be an excess of air, and if 
too thick too little air will enter the furnace, both of which will 
cause a loss for reasons previously explained. This is particu- 
larly true with bituminous coals. Theoretically, therefore, the 
best result would be obtained by firing small quantities at fre- 
quent intervals rather than larger quantities of fuel less often. 
Frequent firing requires that the fire doors be opened often, and 
this means a loss due to too much air entering while the doors 
are open. The practical objection to frequent firing lies in the 
fact that it is difficult to get a fireman who will fire a boiler 
properly, most of the men who perform this kind of labor being 
of the class that prefers shoveling a large amount of fuel into the 
furnace and then sitting down for half an hour than to shoveling 
a lesser amount at shorter intervals. The kind of men who take 
an interest in stoking properly, and do it, are not likely to re- 
main firemen. For the reasons given, the only way in which 
coal can be supplied to a furnace in such a manner as to produce 
the best results is by mechanical means or mechanical stokers. 
There is every reason to believe that a plant of boilers using 
bituminous coal mechanically fired will operate with a sufficient 
economy of fuel over hand-fired boilers to pay a good return on 
the increased investment required for the stoking apparatus. 
This result can be effected by any fireman who is sufficiently 
intelligent to do ordinary firing but not, however, unless the 
mechanical stoker is given some attention to see that holes in 
the fire do not occur or that clinker does not form to impede the 
uniform movement of the coal. The stoker is not wholly auto- 
matic, but, given a fair degree of attention, it is an indispensable 
aid to the firemen in the attainment of the perfect combustion 
of bituminous coal. Mechanical stokers are also of value in 



STEAM POWER PLANTS 209 

reducing smoke with bituminous coal and reducing the number 
of men in the boiler plants. They are of particular value in 
making it possible to burn low-grade smoking coals in situations 
where the emission of smoke would be objectionable. As an 
improper air supply affects the amount of smoke emitted by 
coal, mechanical stokers properly designed very much reduce 
the smoke and oftentimes entirely do away with it. 

Burning Pulverized Fuel. — There is one method of mechani- 
cally supplying coal to boilers that gives promise of much suc- 
cess and that is after pulverization. The principal difficulty that 
has been met in the past has been the expense of pulverizing, but 
recently methods have come into use that make this method com- 
mercially possible. Various types of mills for this purpose have 
been in use in the cement industry, ever since the development 
of the rotary kiln, that have given excellent satisfaction. Bitu- 
minous coal is ground and stored in hoppers from which it is 
delivered usually by a small screw conveyor to a pipe about four 
inches in diameter and terminating in the mouth of the kiln in 
which the cement is burned. A blast of air passing through the 
pipe delivers the coal to the kiln where it burns. The jet of 
flame is six or eight feet long and of such an intensity that it 
could not be introduced directly under a steam boiler, hence a 
boiler would have to be equipped with a detached or separate fur- 
nace to use fuel in this way. One difficulty with this method of 
using pulverized fuel lies in the danger of storing it in quantities, 
and to overcome this machines have been devised to pulverize 
the coal and deliver it directly to the furnace, each boiler being 
equipped with a pulverizer. By pulverizing the fuel the com- 
bustion of all the coal is complete as there is no loss due to the 
falling of fine particles of coal through the grate bars as there 
is in other methods of firing. The relative amounts of air and 
coal supplied can be adjusted to a nicety, hence there is no loss 
through too little or too much air. Furthermore, the coal can 
be burned with absolutely no smoke. 

Supply of Boiler Water. — The amount of water used for 
steam boilers in large plants is of such a quantity that an abun- 
dant supply of good water at low cost is a deciding factor in the 
selection of a site for a power house. The cost of water from city 
mains is usually such that it is desirable for large plants to go 
to some other source, as a river, if one be available, artesian wells, 



210 



STEAM POWER PLANTS 



etc. Before determining upon a supply, investigation should be 
made as to whether or not the water is suitable for boiler pur- 
poses, the opinion of a chemist, not a boiler-compound quack, 
being obtained upon this point. Water may be unfit for boiler 
purposes without treatment on account of the presence of sew- 
age which will cause foaming, or of certain salts which will form 




Fig. 66. Coal Bunkers designed by Sheaff and Jaasted. 

hard scale on the heating surface of the boilers and not only 
impair their efficiency but also entail large expense for cleaning 
them and be a source of probable danger besides. Deep well 
waters frequently contain scale-forming salts and occasionally 
rivers receiving the rainfall from certain watersheds. River 
water is frequently contaminated with sewage. Sewage can 
probably be best removed for boiler purposes by mechanical 
filtration; silt and mud by sedimentation and the same process. 
Water Softening. — The salts which give the most trouble in 
steam-boiler waters by the formation of scale are the carbonates 
and sulphates of lime and magnesia. The presence in water of 
these salts, except the sulphate of magnesia, cause it to be hard, 



STEAM POWER PLANTS 



211 



and their removal is known as water softening. Sulphate of 
magnesia does not cause scale to form, but it is precipitated by 
concentration. Its presence prevents the removal of other salts 
by chemical treatment due to the fact that when lime water is 
added to water containing it, it breaks up and sulphate of lime 
results, which does form scale. A small quantity of carbonate 



Scale 
0' 8' 16' 24 

' ' ' ' » ' i ' ' ■ ' ■ ■ 




Fig. 67. Typical Coal Elevating Tower. 



of lime is apt to remain in solution in almost pure water, but if 
the water be saturated with carbonic acid the amount of carbon- 
ate of lime in solution can be very much greater ; most of it being- 
precipitated when the carbonic acid is driven off, as it is when 
the water is heated. By adding lime water to water containing 
carbonate of lime and carbonic acid, the lime combines with the 
carbonic acid to form carbonate of lime which, with the car- 
bonate of lime previously in the water, is precipitated because 
of the disappearance of the carbonic acid. Carbonate of mag- 
nesia is very similar in its properties to carbonate of lime. It is 
also acted upon by the lime water so as to form hydrate of mag- 
nesia, an almost insoluble salt, and carbonate of lime which is 
precipitated. The removal of the carbonates by the addition 
of lime water was proposed by an English chemist named Clark 
and this process generally bears his name. 



212 STEAM POWER PLANTS 

Sulphate of lime and sulphate of magnesia may be broken up 
by adding sodium carbonate, the former resulting in the forma- 
tion of calcium carbonate, which is precipitated, and sodium 
sulphate, a nonscale-forming salt. The magnesium sulphate is 
split up into sodium sulphate and carbonate of magnesia and 
the latter can be further broken up by adding lime to cause an 
additional reaction in the manner described. The amount of 
sulphate of lime that can be dissolved in water depends upon 
the temperature, but above a temperature of about 100° F. the 
solubility of this salt diminishes. At 300° F. it is said to be 
insoluble. By heating with live steam, therefore, it is possible 
to precipitate nearly all of the sulphate of lime in water con- 
taining it. Quite a little time, however, is required to complete 
the reaction. Heating water carrying sulphate of lime previous 
to its entering a boiler will only remove the excess of sulphate 
of lime over that possible to retain in solution at the temperature 
to which the water is heated, so that unless it is heated to a high 
temperature chemical treatment is necessary to precipitate that 
not precipitated by heating. 

It will be noticed from what has been said that the carbonates 
of lime and magnesia can be mostly removed by heating, particu- 
larly if sufficient boiling occurs to drive off the carbonic acid, and 
some of the sulphate of lime can also be precipitated by heating. 
All of the four salts mentioned can be practically removed by 
chemical treatment. The heating method is more limited in its 
application but it is cheaper when it can be used. In certain 
cases chemical treatment or a combination of chemical treatment 
with the application of heat is alone possible. The best method 
can only be determined by a competent chemist after a proper 
investigation of the water is made, as it depends entirely upon 
the kind and quantity of salts present in the water. 

Purifying with Exhaust Steam. — Almost all of the carbonates 
of lime and magnesia can be precipitated by moderate warming 
such as could be accomplished by exhaust steam in a feed-water 
heater of the open type. These are usually provided with trays 
over which the water trickles and filtering material to intercept 
the precipitated salts that do not lodge on the trays. Care 
should be taken that the heater is large enough to insure a low 
velocity of water passing through it to give time for the precipi- 
tation to occur in the heater and not in the boiler. Very often 



STEAM POWER PLANTS 213 

boiler waters are only objectionable because of the presence of 
salts which could be entirely removed practically in an exhaust- 
steam heater. 

Purifying by Live Steam. — A live-steam purifier is a device 
similar in a general way to most open-type feed-water heaters in 
that it consists of a shell containing a number of trays that can 
be withdrawn by removing the head of the heater, the trays being 
arranged one over the other so that the water trickles slowly 
downward over them so as to become thoroughly heated by the 
live steam under full boiler pressure that is admitted to the 
heater. The heater is usually located over the boilers so that 
water will run from it to the boilers by gravity. As live steam 
is used in these heaters and the temperature is higher, much more 
of the sulphate of lime present in water will be precipitated than 
there will in an exhaust-steam heater. This type of heater will 
eliminate the carbonates of lime and magnesia. 

Purifying by Chemical Treatment. — The chemical treatment 
might be divided into two methods, the intermittent and contin- 
uous systems, and perhaps a third, with either combined with 
the application of heat to the water while being treated for the 
purpose of hastening the action of the reagents. The original 
Clark process was the intermittent method and it has been 
modified more or less by others. Usually this system consists 
of two large settling tanks in which the water to be treated is 
run, the proper amount of chemicals added, the mixture agitated 
and then allowed to stand for some hours while the precipitate 
settles, the clear treated water on top being used and the sludge 
that settles being blown off when necessary. This system usually 
requires two tanks so that the treatment can go on in one while 
purified water is being drawn from the other. An objection to 
it is the first cost. With the continuous method the untreated 
or raw water and the necessary chemicals are mixed in the de- 
sired proportions, the supply of both being relatively constant, 
both being fed into a tank of generous size so arranged that the 
current is sufficiently slow for the precipitate to settle in the 
bottom of the tank, the clear water passing on to the outlet. 
The continuous treatment combined with heat has been used with 
no little success. The Sorge-Cochrane system of water purifi- 
cation consists in heating water almost to the boiling point, 
purifying by a simple chemical treatment and at the same time 



214 STEAM POWER PLANTS 

neutralizing such acids as are present in the water. The supply 
of water to the boilers is made up of all the pure condensation 
that can be saved and utilized, and of just enough fresh cold 
water supplementing this condensation to supply the demand. 
The conversion of the sulphates and carbonates of lime and other 
soluble salts into insoluble and neutral salts is accomplished in a 
specially designed feed-water heater of the open type by intro- 
ducing into the water to be tested, before it enters the heater, a 
suitable chemical such as soda ash and simultaneously heating 
the water. Means are provided for varying the amount of the 
reagent, and also, by means of a filter bed in the heater, of inter- 
cepting the precipitated salts and other insoluble matter. 



INDEX 



Advantages of mechanical draft, 171. 
Allis-Chalmers cross-compound ver- 
tical engine, test of, 66. 
Ample draft, necessity for, 170. 
Anthracite coal, 25. 
Apparatus, life of, table, 13. 

Ball noncondensing engine, test of, 

65. 
Barrus on "Boiler Tests," 17. 
Bearing capacity of soils, 9. 
Beds for engines, 71. 
Bituminous coals, 25. 
Boiler-feed pumps, 157. 
Boiler plants, designing, 20. 
Boiler-room labor, cost of, 205. 
Boiler specifications, 37, 43. 

tests, Barrus on, 17. 

tubes, 32. 

value of a horse-power of, 17. 

water, supply of, 208. 
Boilers, attaining best efficiency, 
15. 

heating surface necessary, 15. 

horizontal return tubular, 27-47. 

horizontal tubular, braces in, 29. 

horizontal tubular, tube spacing in, 
table, 31. 

Manning vertical, 27. 

riveting, 35. 

settings for, 36. 

thickness of shell of, 27. 

types of, 17. 

water-tube, specifications for, 46. 
Bracing horizontal tubular boilers, 

29. 
Building for power house, 6. 

power plants, piping, 111. 
Bulkley siphon-condenser, 148. 
Burning pulverized fuel, 209. 



Capacity of chimneys, 185-193. 
Cast-iron pipes, 132. 
Chemically purified water, 213. 
Chimney linings, 194. 
Chimneys and smoke flues, 42. 

capacity of, 185-193. 

foundations for, 197. 

height of, 181. 

Kent's table of capacities, 185. 

materials for, 197. 

size of, 181. 

steel, 199. 

steel, foundations for, 200. 
Coal-handling machinery, 203. 
Coals, anthracite, 25. 

bituminous, 25. 

characteristics of, 21. 

classification of, 24. 

draft required for various kinds, 
182. 

relative value of, table, 23. 

semibituminous, 25. 
Combustion, draft required for vari- 
ous coals, 183. 

theory of, 169. 
Compound engines, piping for, 109. 
Concrete foundations, 11. 
Condensation in feed-water heaters, 

162. 
Condenser equipment, guarantees 

for, 156. 
Condensers and pumps, 141. 

Bulkley siphon, 148. 

jet type, 150. 

location of, 151. 

saving due to, 142. 

sources of water supply for, 153. 

types of, 144. 

water necessary for, 152. 

Worthington, 146, 148. 



215 



216 



INDEX 



Condensing plants, piping for, 108. 
Construction of power house, 6. 
Cooling towers, 154. 
Corliss engine, specification for, 77. 
Cost of boiler-room labor, 205. 
of engines, 50. 
of equipment, 14. 
of fuel, 50. 

of handling coal by machinery, 205. 
Costs, relative operative of turbines, 

91. 
Covering pipes, 135. 
Cylinder dimensions in specifica- 
tions, 69. 
Cylinders, proportioning for com- 
pound engines, 59. 
proportioning for Corliss single- 
cylinders, 55. 
proportioning for medium-speed 

engines, 59. 
proportioning for single-cylinder 

high-speed engines, 59. 
tables of dimensions of, 57, 58. 

Depreciation of plants, 12. 

rate of, table, 13. 
Design of fans, 174. 
Designing horizontal return tubular 

boilers, 27. 
Draft, advantages of mechanical, 
171. 

induced, capacity table, 179. 

mechanical, 171. 

necessity for ample, 170. 

provision for, 22. 
Drafts, theoretical, table, 182. 
Drawings for piping, 102. 

for plant, 4. 
Drips, care of, 116. 
Duplicating steam piping, 108. 
Durability of turbines, 91. 

Economizers, 164. 

Barrus' tests of, 167. 

Roney's tests of, 167. 
Efficiency of boilers, how to attain, 
15. 



Electric power-house, steam piping 
for, 104. 

work in engine construction, 74. 
Engine, Allis-Chalmers cross-com- 
pound vertical, test of, 66. 

Ball noncondensing, test of, 65. 

construction, electric work in, 74. 

construction, materials in, 72. 

Corliss, specification for, 77. 

foundations, 10. 

oiling systems, 139. 
Engines, beds for, 71. 

compound, mean effective pressure 
for, 60. 

compound, piping between cylin- 
ders of, 109. 

compound, proportioning cylin- 
ders for, 59. 

condensers for, 141. 

cost of, 50. 

McEwen compound single- valve, 
test of, 65. 

mean effective pressure, 53. 

methods for selecting, 48. 

piston speeds, 53. 

proportioning cylinders for com- 
pound, 59. 

proportioning cylinders for me- 
dium-speed, 59. 

proportioning cylinders for single- 
cylinder high-speed, 59. 

proportioning cylinders of Corliss 
single-cylinder, 55. 

rotative speed of, 52. 

specifications for, 68-88. 

steam consumption of different 
types, 49. 

steam pressure, 51. 

tests of simple noncondensing 
high-speed, 64. 

turbine, 89-101. 

variable loads and overloads, 62. 
Equipment, cost of, 14. 
Exhaust-steam turbines, 94. 
Expenses of operating, 12. 

Fans, design of, 174. 
induced draft capacity, table, 179. 



INDEX 



217 



Fans, revolutions necessary to main- 
tain given pressure, table, 178. 

theory of, 173. 

volume of air, power required, etc., 
table, 177. 
Feed-water heaters, 160. 

piping, 117. 
Fire-tube boilers, 18. 
Fittings for steam pipes, 128. 
Flanges, forged-steel, 132. 

schedule of standard, 129. 

schedule of standard for extra- 
heavy steel pipe, 130. 

screwed, 131. 

threaded, 131. 
Flues and chimneys, 42. 

frictional loss, 183. 
Forced draft, 176. 
Foundations for chimneys, 197. 

for engines, 10. 

for power house, 8. 

for steel chimneys, 200. 
Frictional loss in flues, 183, 184. 
Fuel cost, 50. 

pulverized, 208. 

study of, 21. 

Generators, specifications for, 99. 
Grates, importance of proper sur- 
faces, 21. 
ratio of, to heating surface, 22. 
Grease separators, 136. 
Guarantees for condenser equipment, 
156. 

Hangers, 135. 

Hartford Steam Boiler Inspection 
and Insurance Company, rec- 
ommendations, 34, 35. 

Heaters for feed- water, 160. 

Heating surface, division of, in units, 
20. 
steam boilers, 15. 

Height of chimneys, 181. 

Hills, Nicholas S., specification writ- 
ten by, 75. 

Holly system, 116. 



Internally fired boilers, 19. 

Joints, lap, dimensions of, table, 34. 

Kent's table of chimney capacities, 
185. 

Linings for chimneys, 194. 
Load curve of power plant, 16. 
Loads, variable and overload capaci- 
ties, 60. 
Location of condensers, 151. 
of plant, 2. 

McEwen compound single-valve en- 
gine tests, 65. 

Machinery, coal-handling, 203. 

Manning vertical boiler, 27. 

Materials for chimneys, 197. 
in engine construction, 72. 

Mean effective pressures for differ- 
ent steam pressures, table, 
60. 

Mechanical draft, 171. 
stokers, 208. 

Noncondensing plants, feed-water 
piping for, 121. 
piping for, 110. 

Oiling systems, 139. 
Operating expenses, 12. 
Overload capacities, 60. 
capacity of turbines, 90. 

Philadelphia, department rules for 

testing, 27. 
Piles, use of, in foundations, 10. 
Pipe hangers, 135. 
Pipes, cast-iron, 132. 

covering for, 135. 

dimensions of standard-weight, 
123. 

fittings, kind of, 128. 

flanges, 129-131. 

standard sizes, 123. 

steam, sizes of, 124. 
Piping, between cylinders of com- 
pound engines, 109. 

blow-off, 121. 



218 



INDEX 



Piping, care of drips, 116. 

drawings for, 102. 

feed- water, 117. 

for building power plants, 111. 

for condensing plants, 108. 

for noncondensing plants, 110. 

principles involved in, 102. 

specifications for, 133. 
Piston speed, 53. 
Power house, building for, 6. 

foundations for, 8. 

type of, 5. 
Power, transmission of, 3. 
Proper grate surfaces, importance of, 

21. 
Proportioning grate surface, 22. 
Pumps and condensers, 141. 

boiler-feed, 157. 
Purifying water supply, 212-214. 

Reheaters and steam jackets, 67. 
Requisites for proper location, 3-5. 
Riveting, 35. 
Rivet steel, strength of, 35. 



Steam consumption, r guaranty as 
to, 74. 
engine specifications, 68-88. 
exhaust for purifying water, 212. 
flow of, in pipes, 127. 
jackets and reheaters, 67. 
live, for purifying water, 213. 
pipes, covering for, 135. 
pipes, pitch of, 103. 
piping, 73. 
blow-off, 121. 
care of drips, 116. 
drawings for, 102. 
duplicating, 104. 
for building power plants, 111. 
for electric power house, 104. 
pressure, 51, 53, 60. 
separators, 138. 
superheated, 67. 
traps, 138. 
Steel chimneys, 199. 

foundations for, 200. 
Stokers, mechanical, 208. 
Surface condensers, 145. 



Saving due to condensers, 142. 
Seams, dimensions of, table, 34. 
Semibituminous coals, 25. 
Separators, grease, 136. 

steam, 138. 
Settings for boilers, 36. 
Sinking fund, 12. 
Size of chimneys, 181. 

of steam pipes, 124. 
Softening water, 210. 
Soils, bearing capacity of, 9. 
Specifications for boilers, 37, 43. 

for Corliss engine, 77. 

for generators, 99. 

for piping, 133. 

for steam engines, 68-88. 

for steam turbines, 94. 

for water-tube boilers, 46. 

of Nicholas S. Hill, Jr., 75. 
Speed, rotative, of engines, 52. 
Steam consumption of engines and 
turbines, 92. 

consumption, table of, 49. 



Table, air volumes in fan operation, 
177. 

Barms' tests of economizers, 167. 

cost of handling coal by machinery, 
205. 

data of simple noncondensing 
high-speed engine tests, 64. 

dimensions of cylinders and speed 
for high-speed automatic cut- 
off engines, 58. 

dimensions of cylinders and speeds 
of Corliss engines, 57. 

dimensions of double-riveted stag- 
gered seams, 34. 

dimensions of standard-weight 
pipe, 123. 

dimensions of triple-riveted butt 
joint with double welt, 35. 

dimensions of triple-riveted lap 
joint, 34. 

draft in inches of water to burn 
different coals, 183. 

economy tests of steam turbines, 93. 



INDEX 



219 



Table, flow of steam in pipes — de- 
livery in pounds per minute, 
127. 
frictional loss in square iron flues, 

etc., 183. 
in specifications for steam turbine, 

95. 
induced draft capacity for fans, 

179. 
Kent's chimney capacities, 185. 
life of power-plant apparatus, 13. 
mean effective pressures for dif- 
ferent steam pressures, 60 
mean effective pressures for simple 

type engines, 55. 
rate of depreciation of plant, 13. 
relative cost of operating turbines 

and engines, 92. 
relative value of steam coals, 23. 
revolutions of fan necessary to 
maintain a given pressure, 178. 
Roney's tests of economizers, 167. 
schedule of standard flanges, 129. 
schedule of standard flanges for 

extra heavy steel pipe, 130. 
steam consumption of different 

types of engines, 49. 
steam consumption of engines and 

turbines, 92. 
theoretical drafts in chimneys, 182. 
tube spacing and heating surface 
in horizontal tubular boilers, 31. 
water consumption of steam tur- 
bine, 97. 
Testing, Philadelphia rules, 27. 
Tests, economical, of steam turbines, 
93. 
of economizers, 167. 
of various types of engines, 64-66. 
of Westinghouse turbine, 94. 
Theory of fans, 173. 
Towers for cooling condensing water, 
154. 



Traps, steam, 138. 

Tube spacing in horizontal tubular 

boilers, table, 31. 
Tubes, 32. 
Turbines, advantages of, 89. 

durability of, 91. 

economy tests of, 93. 

effect of vacuum and steam pres- 
sure, 92. 

exhaust-steam, 94. 

overload capacity of, 90. 

relative operative costs, 91. 

space conditions, 89. 

specifications for, 94. 

variable loads of, 91. 

water consumption of, table, 97. 

Westinghouse, test of, 94. 
Type of engine to be selected, 49. 

of plant, 5. 

of power house, 5. 
Types of boilers, advantages of, 17. 

of feed-water heaters, 160. 

Value of a boiler horse-power, 17. 

Valves, 134. 

Variable loads of turbines, 91. 

Water consumption of steam tur- 
bine, 97. 

in locating plant, 4. 

purified by chemical treatment, 
213. 

purifying by live steam, 213. 

purifying with exhaust-steam, 212. 

softening, 210. 

supply for condensers, 153. 

supply of, for boilers, 208. 
Water-tube boilers, 18. 

boilers, specifications for, 46. 
Westinghouse turbine, test of, 94. 
Worthington condensing equipment, 
146, 148. 



JAN 26 1912 



One copy del. to Cat. Div. 



2$ ^912 



